* As an English surname, converged from variants of Giles (sometimes through Dutch), Julian, and William.
* As a northern English surname, from Middle English gil (“ravine, glen”), from Old Norse gil. The Old Norse is also a source of the Norwegian surname.
* As an Irish and Scottish Gaelic surname, variant of McGill.
* Also as an Irish surname, variant of Gall.
* As a Jewish/Israeli given name, as well as surname, from Hebrew גיל (“joy”).
* As a German surname, variant of Gilger.
* As a Sikh Punjabi surname originating in India, from ਗਿੱਲ (gill, “moisture”).