What do you say "Amant" in English, a thing or some money you give to somebody so that they will keep it safe for you and return to you when you need or ask for. They keep it for you and do not make any changes to it?
'From my diamond ring I would not part
For it's a token from my sweetheart'
Sovay, (trad., anon.) See more here: Pentangle - Sovay Lyrics
A more general term (for something with no intrinsic value - say, a lock of hair) is 'keepsake' (pronounced like the two constituent words, 'keep' + 'sake'.)