I doubt your source for this is reliable. There is no verbal root amar meaning "eternal" or anything of the kind.
Spelt with an Aleph it means "speak", and there is the personal name Amarja / Amarya ("God has spoken i.e. created" or "promised by God"). (Short form: Imri)
Spelt with an Ayin it means "collect/make sheaves" or else "attack, treat brutally". The name of king
Omri (same verbal root) is supposed to be of Arabic origin (and obscure meaning).
The Hebrew words for "eternal/eternity" are "olam", "netzakh", "ad".
Andy ;—)