"to tickle," mid-14c. (implied in kitellynge), from or parallel to Middle Dutch kitelen, Old High German kizzilon, German kitzeln, Old Norse kitla, all apparently somehow felt as suggestive of the action.
Entries linking to kittle
tickle v.
c. 1300 (implied in tickling) "to touch lightly so as to cause a peculiar and uneasy or thrilling sensation in the nerves," of uncertain origin, possibly a frequentative form of tick (v.) in its older sense of "to touch." Some suggest a metathesis of Middle English kittle, which is from a shared Germanic word for "to tickle," but tickle is attested earlier. The Old English form was tinclian.
Meaning "to excite agreeably" (late 14c.) is a translation of Latin titillare. Meaning "to poke or touch so as to excite laughter" is from early 15c.; figurative sense of "to excite, amuse" is attested from 1680s. The noun is recorded from 1801. To tickle (one's) fancy is from 1640s. Related: Tickler.