lunaryoudaoicibaDictYouDict[lunar 词源字典]
lunar: [17] Latin lūna ‘moon’ came from an Indo- European base which also produced English light (not to mention a range of Latin ‘light’- words, such as lūx and lūmen, which have given English illustrate, lucid, luminous, lustre, etc). It had two adjectival derivatives: lūnāris, which simply meant ‘of the moon’, and was borrowed by English as lunar; and lūnāticus.

This was originally used for ‘living on the moon’, but subsequently came to employed in the sense ‘crazy’, from the notion that certain sorts of periodic madness were caused by the phases of the moon. English acquired it via Old French lunatique as lunatic [13].
=> illustrate, light, luminous, lunatic, lustre[lunar etymology, lunar origin, 英语词源]
lunar (adj.)youdaoicibaDictYouDict
"crescent-shaped," early 15c.; "pertaining to the moon," 1620s, from Old French lunaire (15c.), from Latin lunaris "of the moon," from luna "moon" (with capital L- "moon goddess"); see Luna.