Do you know ghouls from goblins and ghosts?
"nailhead, knob," Old English studu "pillar, prop, post," from Proto-Germanic *stud- (cf. Old Norse stoð "staff, stick," prop. "stay," Middle High German stud, Old English stow "place"), from PIE *stu-, variant of root *sta- "to stand" (see stet). Sense expanded by late 14c. to include ornamental devices fixed in and projecting from a surface. The verb is c.1500 in the literal sense of "set with studs," 1560s in studded with "as though sprinkled with nails with conspicuous heads."
"horse used for breeding," Old English stod "herd of horses, place where horses are kept for breeding," from Proto-Germanic *stodo (cf. Old Norse stoð, Middle Low German stod, Old High German stuot "herd of horses," German Stute "mare"), from PIE root *sta- "to stand," with derivatives meaning "place or thing that is standing" (cf. Old Church Slavonic stado "herd," Lithuanian 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.
[fr stud or studhorse, ''stallion, esp one kept for breeding,'' the term found by 1903; first sense popularized by 1940s jive talk]