Ticklish means sensitive to touch, or awkward to handle. Ticklish feet, a ticklish subject, ticklish negotiations.
The physical sense has a genuine puzzle in it: you cannot tickle yourself, because the brain predicts your own movements and cancels the sensation. The figurative sense means delicate — a ticklish question is one that must be handled carefully or it goes wrong. Note tickle, which is probably imitative.
1adjectiveticklishSensitive to being tickled.
“My little brother is so ticklish that he screams if you touch his feet.”
2adjectiveawkwardAwkward and needing careful handling.
“Asking your boss for a pay rise during job cuts is a ticklish business.”
ticklish is a quality of sensitivity or delicacy.
Middle English
tiklen
English
tickle
English, today
ticklish
From tickle + -ish. tickle comes from Middle English tiklen, tikelen, of unknown 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 frr tigele (“to tickle”) (Hallig dialect), and tiikle (“to tickle”) (Amrum dialect), German dialectal zicklen (“to excite; stir up”). Alternatively, from a metathetic alteration of Middle English kitelen "to tickle"; see kittle. Both are ultimately.
Etymology from Wiktionary, CC BY-SA