Enceinte \en-SEYNT\ , adjective;
1. Pregnant; with child
1. A wall or enclosure, as of a fortified place
According to Etymonline.com:
Enceinte used to be spelled insente and dates to the 1600's. It comes from 12th century French enceinte ("pregnant"), which came from Late Latin incinta ("ungirt"). Incinta is a combination of Latin in- (a privative prefix) + cincta (the feminine of cinctus and the past participle of cingere, meaning "to grind"). The modern form of this word is from the 18th century and is possibly a reborrowing from French.
This use of 'reborrowing' is incorrect. In linguistics, if a word is adopted from a foreign language, phonologically adjusted to the new language, and then the new form is adopted by the original foreign language, it is 'reborrowed'. For clarification, here's an example: the Old French word tenez was adopted (and adapted) into English as tennis, which was adopted into Modern French as le tennis. The word came from French, went through an English filter, and re-entered the French language. Since enceinte originally entered the English language from French influences, it could not be 'reborrowed' in the linguistic sense. What I think they meant was that this word was adopted once as "pregnant" and then, after the French definition had shifted into the current noun version, it was adopted a second, separate, time.
*Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Monday, November 1, 2010