Johnny Rowsers, n. — Green’s Dictionary of Slang

Johnny Rowsers n.

also Charley rousers, Charlie Rousers, jolly rousers

[rhy. sl.]

(US) trousers.

1928		M.C. Sharpe Chicago May: Her Story in Hamilton (1952) 132: Johnny Rowsers – trousers.
1935		A.J. Pollock Und. Speaks 20/1: Charley rousers, trousers.
1949		Monteleone Criminal Sl. (rev. edn).
1953		Berrey & Van den Bark Amer. Thes. Sl. (2nd edn) n.p.: [jolly rousers].