The word haga means e.g. 'bay', an inwards bent part of the coast. Rave is to 'take hold of' etc.

Together haga rave might suggest a bay for achorage. Quite other meanings are, however, not excluded, for instance a fish-trap or bird-cage.

A few preliminary remarks and imaginations:

1. The haga rave glyph type does not show a picture of a 'bay', instead it appears to be an illustration of a bent branch.

Sometimes the implication may be not only bent but rather 'broken' as in Pa5-40:

"The Polynesians mingle the time-indications based on the position of the sun with others which are derived from the life of men and nature. We are told that the Hawaiian day was divided into three general parts, 1, breaking the shadows, 2, the plain, full day, 3, the decline of the day... " (Nilsson)

Pa5-40 could be an allusion to daybreak ('breaking the shadows').

A bent branch can symbolize 'change'. The 'curved' was according to the Pythagorean school a 'female' trait:

“Freeman describres the dualistic cosmology of the Pythagorean school (-5th century), embodied in a table of ten pairs of opposites. On one side there was the limited, the odd, the one, the right, the male, the good, motion, light, square and straight. On the other side there was the unlimited, the even, the many, the left, the female, the bad, rest, darkness, oblong and curved.” (Needham 3)

From this it is clear that there is a high probability for 'curved' to also imply 'darkness' in the minds of the Easter Islanders. This is one reason (among others) to interpret 'breaking the shadows' as going from the female night to the male day.

Night is divided in two parts by midnight. Noon has not the same power of division, because it is the same day before and after noon. Day is male, night is female.

The haga rave glyph type maybe should be understood not only as the object 'bent branch' but also - and primarily - as a symbol for the flexible 'female'. The bent branch is soft and pliant, otherwise it could not be bent at all - under stress it would break to pieces.