"to substitute," 1530s, from Latin subrogatus, variant of surrogatus, past participle of subrogare/surrogare "put in another's place, substitute, cause to be chosen in place of another," from sub "in the place of, under" (see sub-) + rogare "to ask, propose," apparently a figurative use of a PIE verb meaning literally "to stretch out (the hand)," from root *reg- "move in a straight line" (compare surrogate). Related: Subrogated; subrogating.
