Trousers
early 17th century: from archaic trouse (singular) from Irish triús and Scottish Gaelic triubhas (see trews), on the pattern of drawers .
wiktionary
Attested since the 1610s, from the earlier form trouzes (attested since the 1580s), extended from trouse (1570s), with plural ending typical of things in pairs, from Middle Irish triubhas(“close-fitting shorts”), of uncertain origin. The unexplained intrusive second -r- is perhaps due to the influence of drawers. [1]
etymonline
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.
