1A person who uses the left foot more naturally than the right; a person (especially a sportsperson) whose left foot is naturally stronger or more dexterous than the right.
2A kick executed with the left foot. Also (Association Football): a shot, pass, or clearance made by kicking a ball in this way.
3slang (chiefly depreciative). A Roman Catholic; (also occasionally) a Protestant.
Mid 19th century; earliest use found in The Times. From left + foot + -er, after left-footed.