• lustrum •
Pronunciation: lê-strêm • Hear it!
Part of Speech: Noun
Meaning: 1. A ceremony to purify all the Roman people conducted every five years after the census had been taken; the census itself. 2. A period of four or five years, hence a collegiate lustrum.
Notes: Today's Good Word comes from a rather odd Latin word, but it brought with it an adjective, lustral "quinquennial, occurring every (four or) five years". It also brought along its Latin plural, lustra, which is now optional—these days we are permitted to use lustrums. If you are thinking it must be related to luster (British lustre), you are right for reasons we will get into in the Word History.
In Play: Lustrum usually refers to period of five years (a quarter score of them): "After a lustrum in New York, Ginger Schnapps decided she didn't like it there and returned to Germany." However, since college years are grouped into approximately that number, it is used to refer to the (usually) four years of matriculation there: "Ray Scane dropped out of PU in the middle of his lustrum there."
Word History: Today's Good Word ran off its semantic rails on its way to English. It started out in Latin meaning "washed", and from there moved on to "purified". Purificatory ceremonies often involved ablutions, the washing of some part of the body: feet, head, hands. It was the past participle of the verb luere "to wash, cleanse, purge", a verb that merged with lavare "to wash" later on in Latin. Lustrum remained only as a name of the purificatory ceremony, which went on to become what it means today. A new verb was then created from lustrum: lustrare "to purify", which came to mean "brighten, make lustrous". This is how the Latin word came to English, via French lustre, as luster. By the way, the same PIE word may be found in Lucifer. Lucifer was originally the light-bearer, from Latin lux (luc-s) "light, illumination" + fer- "to bear, carry"; the word originally referred to the Morning Star. (We cannot delay a lustrum of anything to extend our gratitude to Timothy Knox for supplying us with today's very Good Word.)