The only free and comprehensive online etymological dictionary of the Spanish language
gracia f. (Noun) "grace," "favor;" (plural) "thanks"
12th cent. From Latin gratia 'id.' From gratus "pleasing" (see grado (2)).
Also the origin of the surnames Gracia and Gracián (from the Latin name Gratianus, from Gratius). As regards the origin of Gracia, a district of Barcelona, it derives from the name of a local Carmelite convent called Nostra Senyora de Gràcia in Catalan.
Indo-European
Romance
Asturian gracia, Portuguese graça, Catalan gràcia, French grâce, Italian grazia, Romanian grație

In Roman society, grace was as much a religious as economic relief. "[Latin] gratia consists in saving expenditure. ...In a money-based civilization “grace” shown to a person is to “show grace” to him by suspending his obligation to pay for the service received. This is how a term of sentiment came to be used in an economic sense, without altogether severing itself from the religious context in which it arose." ~ E. Benveniste, Indo-European Language and Society (1973)