O.E.
gat "she-goat," from P.Gmc.
*gaitaz (cf. O.N.
geit, Ger.
Geiß, Goth.
gaits "goat"), from PIE
*ghaidos "young goat," also "play" (cf. L.
hædus "kid"). The word for "male goat" in O.E. was
bucca (see
buck) until late 1300s shift to
he-goat, she-goat. (
Nanny goat is 18c.,
billy goat 19c.). Meaning "licentious man" is attested from 1675. To
get (someone's) goat is from 1910, perhaps with notion of "to steal a goat mascot from a racehorse," or from Fr.
prendre sa chèvre "take one's source of milk."
[goht] 
) Astronomy, Astrology. the constellation or sign Capricorn.