dissimilitude (n.)

"unlikeness, want of resemblance," early 15c., from Latin dissimilitudinem (nominative dissimilitudo) "unlikeness, difference, dissimilarity," from dissimilis, from dis- "not" (see dis-) + similis"like, resembling, of the same kind," from Old Latin semol "together," from PIE root *sem- (1) "one; as one, together with."