Why is the ninth month called September?
Old English abidan, gebidan "remain, wait, delay, remain behind," from ge- completive prefix (denoting onward motion; see a- (1)) + bidan "bide, remain, wait, dwell" (see bide). Originally intransitive (with genitive of the object: we abidon his "we waited for him"); transitive sense emerged in Middle English. Meaning "to put up with" (now usually negative) first recorded 1520s. Related: Abided; abiding. The historical conjugation is abide, abode, abidden, but the modern formation is now generally weak.