A somewhat dated or stylized loanword from French, used especially in older literature or to evoke a French atmosphere. In modern casual Japanese, 友達 or 友人 are far more common.
from French ami, amie
彼は私の古いアミだ。
He is an old friend of mine.
網 (あみ) means 'net' and is a completely different, everyday word, while アミ (also read あみ) is a rare loanword meaning 'friend'.
krill
Neomysis awatschensis (a species of mysid shrimp) · Neomysis intermedia (a species of mysid shrimp)
Borrowed from French 'ami' (friend).