the quality or state of being crazy, irrational, or mentally unstable.
From 'crazy' (possibly from Middle Dutch 'kraze' meaning to break or shatter), plus the suffix '-ness' (Old English, meaning state or condition).
Medieval English speakers didn't have the word 'crazy'—they used 'mad' or 'witless,' but the Dutch borrowed word 'crazy' (something that's been broken or shattered) only became common English in the 1600s, showing how new words fill emotional gaps in language.
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