gal (n.) Look up gal at Dictionary.com
slang pronunciation of girl, 1795, originally noted as a vulgarism (in Benjamin Dearborn's "Columbian Grammar"). Compare gell, 19c. literary form of the Northern England dialectal variant of girl, also g'hal, the girlfriend of a b'hoy (1849). Gal Friday is 1940, in reference to "Robinson Crusoe."