"a point," 1743, from Latin cuspis (genitive cuspidis) "point, pointed end," a word of unknown origin. In English from 1640s as cuspis. As "a cuspid tooth" by 1828. Related: Cuspidate (adj.), which is attested from 1690s; cuspidal.
curvity
curvy
cushion
cushy
cusp
cuspid
cuspidor
cuss
custard
custodial
custodian