1580s, noun ("person who acts madly or wildly") and adjective ("wild, harum-scarum), from mad (adj.) + cap, used here figuratively for "head." Related: Madcappery. Compare mad-brain "rash or hot-headed person" (1560s).
madcap escapades
mad
Madagascar
madam
madame
madarosis
madcap
madden
maddening
madder
madding
maddish
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