"periodically recurring sexual excitement in animals; animal mating season" (originally of deer), early 15c., from Old French rut, ruit, from Late Latin rugitum (nominative rugitus) "a bellowing, a roaring," from past participle of Latin rugire "to bellow" (from PIE imitative root *reu-). If so, the notion is of the noise made by deer at the time of sexual excitement. The noun rut "roar of the sea" (1630s) in Scottish and persisting in New England dialect is of uncertain connection.
early 15c., "pleasing excitement," from Latin titillationem (nominative titillatio) "a tickling," noun of action from past-participle stem of titillare "to tickle," a word imitative of giggling.
1726, "a drawing or gathering into folds or wrinkles," from pucker (v.). In 18c.-19c. sometimes also in a figurative sense, "state of agitation, condition of excitement" (1741).