Lunacy
来自Big Physics
mid 16th century (originally referring to insanity of an intermittent kind attributed to changes of the moon): from lunatic + -acy.
wiktionary
From lunatic + -cy.
etymonline
lunacy (n.)
1540s, "condition of being a lunatic," formed irregularly in English from lunatic (q.v.) + -cy. Originally in reference to intermittent periods of insanity, such as were believed to be triggered by the moon's cycle. The Old English equivalent was monaðseocnes "month-sickness." In later legal use, any unsoundness of mind sufficient to render one incapable of civil transactions or management of one's affairs. Weakened figurative sense "act of madness or folly" is from 1580s.
