The symbol was first used by William Rowan Hamilton in the form of a sideways wedge ... Another, less-common name for the symbol is atled (delta spelled backwards), because the nabla is an inverted Greek letter delta. In actual Greek usage, the symbol is called ανάδελτα, , which means upside-down delta.

The source of the name may come from the Persian word 'del' ... (pronounced del and meaning 'heart') as the nabla shape is similar to the heart's shape in profile ... It is the name of an Egyptian harp, which was of that shape." (Wikipedia)

The word anádelta - upside-down delta - reminds me of the upside-down king, 'Bringer of Spoils' (cfr at Boanerges), Anax, and of my idea of a connection with Anakena. When the Sun King arrives there, to the beautiful sandy beach in the center of the northern coast, it should be the beginning of a new year, because both children will see the light there:

... They anchored the canoe in the front part of the bay, in Hanga Rau. The canoe of Ava Rei Pua also arrived and anchoraged. After Hotu's canoe had anchoraged, the child of Vakai and Hotu appeared. It was Tuu Maheke, son of Hotu, a boy. After the canoe of Ava Rei Pua had also arrived and anchoraged, the child of Ava Rei Pua was born. It was a girl named Ava Rei Pua Poki ...

The canoes anchoraged in the front part of the bay, they stood still as if coordinated with a solstice. He Anakena is the 1st month on Easter Island and south of the equator it is midwinter, i.e. north of the equator it is midsummer, where Sun turns around to go south. The front part of the bay should be when the Lord 'Giver of Bread' (i.e. the ruler of the front side of the year) is being born.

At the same time north of the equator the rule turns over - as if we were in ancient Sparta - to the King 'Bringer of Spoils' (the ruler of the back side of the year). It is midsummer and he rules July and the following months. Therefore the translation of He Anakena as 'July' should be correct.

Beyond zenith comes descent. Gemini is located in the 8th hour (and the symbol 8 illustrates a pair). The string instrument in the center of Gemini is a Sign which possibly is meant to tell us that 'eating' (kai) is in the past, no longer outside in the open but inside between the Heavenly Twins.

String games are kaikai (with double kai meaning not kai). Full moon is Omotohi = 'the sucking is cut off' and for Sun there is a parallel point where 'his eating is strangled'. Moon sucks and Sun eats when growing. Input is finished for Moon by a knife (a Sun instrument) while the advance of Sun gets entangled.

The form of the nabla symbol - delta inverted - probably alludes to the 'mouth of the River', primarily to the delta of the Nile; this is where the flow of the River is ebbing out in a wealth of small streams and lush vegetation:

The Gemini constellation has 'its feet' in the Milky Way, but the rest is outside. The twin stars Castor and Pollux are free from the 'River', the heads of the Heavenly Twins are outside, they have just been released from the 'Mouth of the River'.