"Rapa Nui and Ra'ivavae are the only Polynesian islands where the term akuaku or a'u and a'ua'u respectively is applied to numinous beings which are believed in by the islanders, from time immemorial up to this day, at least on Rapa Nui.

To the best of our knowledge, Pukapuka in the northern Cook Islands is the only other island where there is a 'lesser ancestral god' or atua tangata named Te Akuaku said to have been a 'foreign god who came from Akalava (Mangaia?)'.

According to the Rapa Nui dictionaries, akuaku means 'noise when swallowing', 'ambition', 'soul, shade, ghost, specter, immaterial, spiritual'. ..."

"... there is no literary or lexical evidence from Rapa Nui which allows for a more precise definition of the term akuaku, and the present day inhabitants of the island are completely unaware of the semantics of the word. We are compelled, therefore, to compare the Rapa Nui evidence with that of other Polynesian islands, in order to determine the basic meaning of the word akuaku and thus, gain an insight into the underlying idea of the phenomenon so denominated."

"The word akuaku occurs semantically cognate in several Polynesian languages. In Mangareva we find it as an adjective meaning 'thin; slender' 'said of men and women only' and the Marquesan dictionary says 'mince, fluet; 'enana akuaku, homme fluet'.

About the phonetically corresponding and semantically similar Tongan form of the word Churchward says: a'ua'u, ... (of persons) old and feeble, more or less decrepit, ... a stage beyond luku. And luku, again is defined as 'old and weak: of persons, horses, and boats, but not of trees or houses'.

The older dictionary by Rabone has au (a'u) meaning 'old people; weak and aged persons' or 'old, ripe'.

Desmedt, in speaking of Mangareva, comments on the term akuaku and relates it explicitly to that of Rapa Nui when he says:

le terme courant par lecquel on désignait ces esprits-fantômes change avec les archipels: Tahiti, les Marquises, les Gambier ont leur mot différent et l'Ile de Pâques est seule à les nommer aku-aku. Or, il semble que le sens étymologique de akuaku soit 'mince'.

Dans la langue des Gambier, si proche de celle de  l'Ile de Pâques, aku-aku veut dire 'mince, en parlant des personnes' ...; en marquisien, aki-aki signifie aussi mince, fin ...

N'est-ce pas que cette étymologie répond à la fois à l'idée des insulaires: esprits = spectres n'ayant que des côtes .., et aux formes si émaciées des statuettes anciennes?

This view is appreciated by Emory who makes the following comment:

G. Maurice Desmedt reveals himself a keen thinker ... he has performed a service of real value, and in bringing out clearly the identity of Easter Island mortuary practices with those of Mangareva he has forged one more link in the chain which binds Easter Island to the basic culture of Eastern Polynesia.

Roussel provides the following description of the appearance of the akuaku in the eyes of the Rapa Nui people:

Quelle idée se faisaient-ils des âmes ou des esprits? Ce n'est pas très clair. C'était, selon eux, quelque chose de subtil, une espèce de spectre sans tête, revêtu seulment de côtes.

and Métraux, on the basis of Roussel's statement just quoted, sympathizes with Desmedt when he remarks:

The name akuaku, now used indiscriminately for lesser gods and spirits, must have meant originally only ghosts or spirits of the dead, although it is not found elsewhere in Polynesia with this meaning. Desmedt ... considers the Easter Island term akuaku cognate with the Mangarevan akuaku, which means 'thin, speaking only of men and women'. This parallel is supported by the Easter Island idea in which ghosts resemble emaciated men.

A still more detailed account of the Rapa Nui beliefs as to the appearance of akuaku in this sense has been recorded from Arturo Teao by Englert. It is the story of the 'ariki Tu'u ko Iho seeing two akuaku, Hitirau and Nuko te Mago who were asleep, and reads in its here relevant parts as follows: ... "

In Legends of the South Seas there is an English version The Story of the Wooden Images. The version in Bierbach, Los Mo'ai Toromiro del 'ariki Tu'u Ko Iho, is in the original Rapanui language with translation into Spanish.

"In order to establish an etymology for the Rapa Nui term akuaku or a'ua'u as applied to ghosts, a display of the lexical evidence from all parts of Polynesia is required ... we do not share Blixen's preference for its derivation from the PPN word *haku ... Therefore we concentrate on the alternative possibility of deriving it from the PPN root *aku meaning 'scrape out with hands', which Blixen disqualifies.

In our opinion this root is derivable from the POC *aku 'scrape out with hands' and the PAN *Ta(N)kur meaning 'scrape out with hands'.

The reflexes of this PPN root with identical or similar meanings are to be found in practically all Polynesian languages. To start with, there is the Maori word aku or akuaku, said to mean 'to clear out an oven by removing the stones, before heating' and 'scrape out, cleanse'.

According to Davies the Tahitian au - which ought to be spelled a'u - signifies 'to scrape together or heap up rubbish'.

For Rapa Nui we find: akui 'to rub, to scrub; to sharpen, to put an edge on; to brush, to daub, to paint, to grease, to anoint ...'

For Rarotonga we have a'u (ahu) 'a plane, such as a carpenter's plane: v. t. to make a surface, as of wood; level or smooth by means of a plane ...'

and the Samoan dictionaries define au and its reduplicated form auau, i.e. a'u and a'ua'u, as 'nettoyer en creusant (to pick)' or 'to scrape the dirt from the hole of the fresh planted taro, and to press down the tigapula'.

In Tonga we find auau or 'au'au, certainly more correctly, a'ua'u, signifying 'to shell; to pick out bones' or 'dégraisser, ôter lenveloppe ou l'écorce, écosser, écorcer ...' and aku, 'gratter (vieux mot)'.

In Niue there is aku 'to shovel up (as gravel, rubbish, etc.), to dig up ... akuaku ... to dig up; ... maakuaku ... dug up (as by a rat)'. That the Niuean word is used in the sense of scraping becomes clear in the sentence: Mo e akuaku aki we tau hui haana e mena ne tu ai a ia: '(the horse) scraped with his hooves the place where he was standing'.

The Rennellese verb aku means 'to excavate, dig, shovel, as the ground oven; to ransack, as the contents of a bag ...' and its reduplication, akuaku, is rendered 'to scratch or dig a little but repeatedly, as chickens or dogs do ...'

The Tikopian noun aku means 'handful' and the verb akuaku 'collect, take up in handfulls ...'

Stimson & Marshall give for the Tuamotuan island of Fagatau maku 'to scoop out a groove as in working a log' and poetically for the Tuamotus as a whole 'to cleave the surface of the sea; as the prow of a ship, the fin of a shark ...'

The Rotuman dictionary lists the following: a'u, 'to scratch ... to dig, dig for, dig up; to investigate minutely'

and in Gilbertese we find: au, auau 'to extract, to pull out of a cavity from under or within, to pull cord out of hole in canoe making ... te auau: act of extracting ... fishing under rocks ... auta: to pull out, to withdraw from, to extract'.

Finally, we quote the Fijian yaku which is translated as: 'to take soft wood with the fingers instead of with a spoon ... yakuta and yaku-raka, remove with the fingers, as a fly from tea, or to take handfuls'.

Through the detailed presentation of this material it is evident that the PPN *aku and its reflexes in the different Polynesian languages and beyond are phonetically and semantically cognate and often identical.

Besides a number of rather more secondary significations, their basic ones are: to scrape, to scoop, to scratch, to rub, to scrub, to shave, to cut, to shovel, to dig and to plane. Actions expressed by these verbs are carried out to remove, to withdraw, to extract, to excavate, to hollow out, to clear out, to cleanse or to smoothen.

All actions and their effects are explicitly or implicitly reducing, diminishing, weakening or even annihilating and appear, therefore, as cognates with the Marquesan, Mangarevan and Tongan words akuaku or a'ua'u which refer to thin, meager, weak, feeble or even decrepit, hence physically reduced persons and, in the last analysis, to such phenomena as the Rapa Nui akuaku or ghosts and the Ra'ivavean 'spirits' called a'ua'u.

This etymology of the term akuaku or the cognate a'ua'u becomes still more plausible and convincing after the analysis of the term varua and a description of the Polynesians' handling of corpses, which we propose to provide subsequently."

(Bierbach)

As to 'handling of corpses', see a short 'extract' from Bierbach about the mummification process.