Polynesian tattoo symbol: gourd

The ipu is one of the basic and most known symbols in Marquesan tattooing.
It has several meanings, all related to genealogy and fertility.

There are several theories about the origin and symbolism of the ipu, and most agree that it has evolved from a representation of the world:

a is the original depiction, with the celestial void and the sheltering sky on the outside, and the earthly womb in the center.
b, c and d show how the original design may have evolved to the final version.

Looking at different designs from wooden carvings though, there is one specific version of etua (divinity or deified ancestor) that attracts the eye and suggests a different origin for the symbol:

Given that the ipu was used in tattooing to represent ancestors and to collect their mana transferring it onto the tattooed person, it seems very likely that the symbol actually may have stemmed from the representation of a deified ancestor upholding his descendants.
The gourd was used as a container, and the symbol representing the ancestor becomes a container itself, hence its name.
The head is simplified and the legs and arms join above the head incorporating the smaller enata and becoming closed circles representing a barrier, a container that collects the mana and keeps it from dispersing.

This seems to be even more likely if we look at another symbol, ouhoi (yam leaf), that looks very similar both to the ipu and to the etua, which is not surprising if we consider that in some legends the yam plant is regarded as an ancestor of mankind:

Rows of coupled ipu symbols were placed along the arms and sometimes legs to represent genealogy, each couple representing two ancestors, with their placement and size indicating their importance.

The position may be due to the need of collecting power, mana, in arms and legs, to make them stronger and more protected, since those parts possess less mana compared to the body and the head, and have more chances to get in contact with either impure or sacred elements, two circumstances that may alter one's balance.

Being related to ancestors and descent, the ipu is also a common symbol for fertility and prosperity.

The rows of ipu under the arm in this photo from 1880 represent ancestors:

The ipu below the enata in this tattoo represents descendants protected by the two facing tiki:

Being this a tattoo for a sailor, the gourd containing the good winds was placed between the sky above and the waves below:

These coupled ipu symbols where incorporated into a turtle symbolizing family:

You can click on the photos to read the full description of each tattoo.