Gratuity, n.; pl. Gtratuities.
Etymology: [F. gratuité, or LL. gratuitas.]
1. Something given freely or without recompense; a free gift; a present. Swift.
2. Something voluntarily given in return for a favor or service, as a recompense or acknowledgment.
Shades of meaning
Fernald has no entry of its own for gratuity; he lists it under gift.
Where he writes about it:
A gratuity is usually something of moderate value and is always given as to an inferior, and as of favor, not of right; as, a gratuity to a waiter. — from gift
Largess is archaic for a bountiful gratuity, usually to be distributed among many, as among the heralds at ancient tournaments. — from gift