1560s, "disputation," from Late Latin litigationem (nominative litigatio), noun of action from past participle stem of Latin litigare "to dispute, quarrel, strive," from phrase litem agere, from litem (nominative lis) "lawsuit, dispute, quarrel, strife" + agere "to drive, conduct" (see act). Meaning "act of carrying on a lawsuit" is from 1640s.