Louie, n.¹ — Green’s Dictionary of Slang

Louie n.¹

[? Fr. coin, the pre-Revolutionary louis d’or, synon. for the écu of the 17C–18C]

(orig. US) $1, in pl. louis, money.

[1890		Sporting Times 8 Feb. 3/2: When I wondered how many louis it was to be, only charged me, or I should say, Boxer, a single franc].
1902		Ade Forty Modern Fables 189: A careful Perusal of our Book: ‘How to stay Pretty.’ It comes to Ten Louies.