Green’s Dictionary of Slang

1. a Roman Catholic, but used in reverse by Catholics who define themselves as right-handers; thus dig with the left foot, to be a Catholic [? turf-cutting spades, as used by Catholics, having the lugs – that piece upon which the foot presses down – on the left of the haft. Note Pennsylvania use left-winger, a Roman Catholic].

1933		C.W. Willemse Cop Remembers 73: He’s a left-footer. He’s Dutch anyhow.
1959		I. & P. Opie Lore and Lang. of Schoolchildren (1977) 396: In Lancashire Roman Catholics are known as ‘Micks’, and in Dundee as ‘Left-footers’.
1990		Pratchett & Gaiman Good Omens (1991) 27: He quite liked nuns. Not that he was a, you know, left-footer or anything like that.
2000		T. Udo Vatican Bloodbath 98: All part of my cunning masterplan to feed Johnny Left-footer so much bullshit he won’t know whether he’s coming or going.

2. a male homosexual.

1989		T. Blacker Fixx 203: The left-footers, the incidents in the urinals at Piccadilly Circus.
2003		McGill Reed Dict. of N.Z. Sl.