farewell gift; parting present
A gift given to someone who is leaving on a journey, moving away, or retiring. Often money or a small present.
I gave a farewell gift to a colleague who is transferring.
I received a book gift card as a parting present.
From 餞 (sen, 'farewell gift') + 別 (betsu, 'parting'). The exact historical derivation is uncertain, but the kanji compound directly conveys the meaning of a parting gift.