My wife is Gillian shortened to Gill (both with soft G's) - an alternative spelling of Jillian; her maiden name was Gill (hard G). There's an author also Gil Gil. The hard G is usually written Gil as in Gil (Gilbert) Houston ie Cisco.
For those old enough a Gill (soft) was one quarter of a pint. However in the North of England if you asked for a Gill of Beer, you'd get a half pint but the milkman would bring quarter of a pint. Much better and easier than those silly metric measure.

Doc John