"nailhead, knob," O.E. studu "pillar, prop, post," from P.Gmc. *stud- (cf. O.N. stoð "staff, stick," prop. "stay," M.H.G. stud, O.E. stow "place"), from PIE *stu-, variant of base *sta- "to stand" (see
stet). Sense expanded by 1397 to include ornamental devices fixed in
and projecting from a surface. The verb is 1505 in the literal sense of "set with studs," 1570 in studded with "as though sprinkled with nails with conspicuous heads."
stud"horse used for breeding," O.E. stod "herd of horses, place where horses are kept for breeding," from P.Gmc. *stodo (cf. O.N. stoð, M.L.G. stod, O.H.G. stuot "herd of horses," Ger. Stute "mare"), from PIE base *sta- "to stand" (cf. O.C.S. stado "herd," Lith. stodas "a drove of horses;" see
stet). Sense of "male horse kept for breeding" is first recorded 1803; meaning "man who is highly active and proficient sexually" is attested from 1895; that of "any young man" is from 1929.