It may be coincidence, but probably it was a wordplay by Metoro when he said ero (resembling hero) at the first glyph documenting early dawn in the 'day calendar' according to Tahua:

Aa1-16	Aa1-17
ka ero	ka tapamea

The Polynesian languages are much like playgrounds, however, and we must not dismiss hiero = to shine, to appear (of the rays of the sun just before sunrise). He hiero te raá, dawn breaks.

The yellow of ripe bananas (hero) and the rays of the sun immediately before sunrise (hiero) have a lot in common, though not obvious for other than Polynesian minds. The common denominator may well be a word ero, now no longer used.

A wordplay with vero ('the black cloth') may also be involved, where vero would be 'death' and hero 'birth'.