Etymology
From Middle English kitelen, from Old English citelian (“to tickle”), from Proto-West Germanic *kitilōn, from Proto-Germanic *kitilōną, frequentative form of Proto-Germanic *kitōną (“to tickle”), from Proto-Indo-European *geyd- (“to stick, jab, tickle”).
Cognate with Dutch kittelen, kietelen (“to tickle”), Low German kettelen, ketelen (“to tickle”), German kitzeln (“to tickle”), Icelandic kitla (“to tickle”), Swedish kittla, kittsla, Danish kilde and perhaps Old Armenian կիծ- (kic-, “to sting, bite”), but note that many such words are sound-symbolic. Compare tickle.