Sensitive to being tickled, or used figuratively to mean tricky, sensitive, or requiring careful handling.
From Middle English 'tickelen' meaning to tickle, combined with '-ish' (having the quality of). The literal sense developed first from Old English, and the figurative 'touchy' meaning emerged in the 16th century.
Your ticklish spots are actually a sign of sophisticated nervous system wiring—the same neural pathways that detect danger and threats are hypersensitive in places like your armpits and feet, which is why those areas make you laugh uncontrollably.
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