early 15c., prorogen, "to prolong, extend" (a truce, agreement, etc.), a sense now obsolete, from Old French proroger, proroguer (14c.) and directly from Latin prorogare, literally "to ask publicly," from pro "before" (see pro-) + rogare "to ask, inquire, question; ask a favor," also "to propose (a law, a candidate);" see rogation. Perhaps the original sense in Latin was "to ask for public assent to extending someone's term in office."
The parliamentary meaning "discontinue temporarily, adjourn until a later time without dissolution" is attested from mid-15c. Related: Prorogued; prorogation.