- lustrum (n.)
[lustrum 词源字典]
- (plural lustra), "purification of the Roman people every five years," 1580s, from Latin lustrum, perhaps from root of luere "to wash," related to lavere (see lave). Or [Watkins, Klein] from PIE *leuk-stro-, from base *leuk- "light, brightness."[lustrum etymology, lustrum origin, 英语词源]