trousers (n.)

"garment for men, covering the lower body and each leg separately," 1610s, earlier trouzes (1580s), extended from trouse (1570s), with plural ending typical of things in pairs, from Gaelic or Middle Irish triubhas "close-fitting shorts," of uncertain origin. Early recorded use of the word indicates the garment was regarded as Celtic: "A jellous wife was like an Irish trouze, alwayes close to a mans tayle" [1630]. The unexplained, unetymological second -r- is perhaps by influence of drawers or other words in pairs ending in -ers.