Etymology
1. c.1330 (intrans.) "to be thrilled or tingling," of uncertain origin, possibly a frequentative form of tick (2) in its older sense of "to touch." The OE form was
tinclian. Some suggest a metathesis of
kittle (M.E.
kytyllen), from Du.
kietelen, from a common North Sea Gmc. word for "to tickle" (cf. O.N.
kitla, O.H.G.
kizzilon, Ger.
kitzeln). Meaning "to excite agreeably" (c.1386) is a translation of L.
titillare. Meaning "to touch lightly so as to cause a peculiar and uneasy sensation" is recorded from 1398; that of "to poke or touch so as to excite laughter" is from 1423; fig. sense of "to excite, amuse" is attested from 1688. The noun is recorded from 1801.
Ticklish in the lit. sense of "easily tickled" is recorded from 1598, later than the fig. sense (1581); an earlier word for this was
tickly (1530).
Tickled "pleased, happy" is from 1586.
2. From Middle English tiklen, tikelen, of uncertain origin. Perhaps from a frequentative form of Middle English tikken (“to touch lightly”), thus equivalent to tick + -le; or perhaps related to Old English tinclian (“to tickle”). Compare North Frisian tigele (“to tickle”) (Hallig dialect), and tiikle (“to tickle”) (Amrum dialect), German dialectal zicklen (“to excite; stir up”).
3. Alternatively, from a metathetic alteration of Middle English kitelen ("to tickle"; see kittle). Both are ultimately sound-symbolic. See: Old English '
tinclian', Frisian, Northern 'tigele'.