divide (n.)

1640s, "act of dividing," from divide (v.). Meaning "watershed, separation between river valleys" is first recorded 1807, American English.

divide (v.)

early 14c., from Latin dividere "to force apart, cleave, distribute," from dis- "apart" (see dis-) + -videre "to separate," from PIE root *weidh- "to separate" (see widow; also see with).

Mathematical sense is from early 15c. Divide and rule (c. 1600) translates Latin divide et impera, a maxim of Machiavelli. Related: Divided; dividing.