Fido

From Spanish or Italian fido from Latin fīdus (“faithful”). Popularly claimed to be directly from Latin fīdō (“to trust, rely on”) instead of the Romance intermediary, but this might be folk etymology. The stereotypical dog's name is evidently very old; a newspaper from 1760 cites, "[a] small white Greyhound with a Collar, answers to the Name of Fido."