euergesy
A good deed, an act of public benefaction by a wealthy individual.
[...] Macedon, and that the attested proxeny and euergesy of Alexander resulted from this invaluable assistance towards the creation of the Athenian war fleet.
Where it comes from
From Ancient Greek εὐεργεσία (euergesía).
Adapted from the Wiktionary entry euergesy (CC BY-SA 4.0).