lest

Meanings

1. 1
   conj

   For fear that; that not; in order to prevent something from happening; in case.

   He won't go outside, lest he be eaten by those ravenous eagles.

2. 2
   conj

   that (without the negative particle; introduces the reason for an emotion.)

   There was danger/alarm lest the plan become known.

Etymology

c. 1200, contracted from Middle English les te (“less that”), from Old English þȳ lǣs þe (“whereby less that”), from þȳ (instrumental case of demonstrative article þæt (“that”)) + lǣs (“less”) + þe (“that,” relative particle). The þȳ was dropped and the remaining two words contracted into leste.