1610s (intransitive), from Latin litigatus, past participle of litigare "to dispute, carry on a suit," from phrase litem agere "to drive a suit," from litem (nominative lis) "lawsuit, dispute, quarrel, strife" (which is of uncertain origin) + agere "to set in motion, drive forward" (from PIE root *ag- "to drive, draw out or forth, move"). Transitive sense is from 1741. Related: Litigated; litigating.