What word or phrase does your mother always say?
trousers, 1840, see pantaloons. Colloquial singular pant is attested from 1893. To wear the pants "be the dominant member of a household" is first attested 1931. To do something by the seat of (one's) pants "by human instinct" is from 1942, originally of pilots, perhaps with some notion of being able to sense the condition and situation of the plane by engine vibrations, etc. To be caught with (one's) pants down "discovered in an embarrassing condition" is from 1932.
mid-15c., perhaps a shortening of Old French pantaisier "gasp, puff, pant, be out of breath, be in distress" (12c.), probably from Vulgar Latin *pantasiare "be oppressed with a nightmare, struggle for breathing during a nightmare," literally "to have visions," from Greek phantasioun "have or form images, subject to hallucinations," from phantasia "appearance, image, fantasy" (see phantasm). Related: Panted; panting.
"a gasping breath," c.1500, from pant (v.).
v. pant·ed, pant·ing, pants
To breathe rapidly and shallowly.
ants, cream one's jeans, fancy pants, fly by the seat of one's pants, fudge one's pants, get the lead out, have lead in one's pants, high waters, hot pants, raggedy-ass, seat-of-the-pants, shit one's pants, smarty-pants