Black pants that are the bottom part of a suit that cover your legs and that you wear to work are an example of trousers.
Origin of trouserslengthened (prob. modeled on drawers) from obsolete trouse from Gaelic triubhas, trews
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.