Source : Webster's Revised Unabridged Dictionary (1913)

Jacchus \Jac"chus\, n. [NL., fr. L. Jacchus a mystic name of
   Bacchus, Gr. ?.] (Zo["o]l.)
   The common marmoset ({Hapale vulgaris}). Formerly, the name
   was also applied to other species of the same genus.