Originally: flavoured or perfumed with ambergris. Later also: resembling or evoking the smell of ambergris (or sometimes perhaps of amber).

Resembling amber in colour; (translucent) yellowish-brown or golden.

Of an insect, especially a fly: preserved in amber. Frequently (and in earliest use) figurative or in similative contexts; compare "like a fly (also insect) in amber". Hence more generally: preserved as though in amber; unchanging; enduring.