extempore (adv.)
1550s, from Latin phrase ex tempore "offhand, in accordance with (the needs of) the moment," literally "out of time," from ex "out of" (see ex-) + tempore, ablative of tempus (genitive temporis) "time" (see temporal). Of speaking, strictly "without preparation, without time to prepare," but now often with a sense merely of "without notes or a teleprompter." As an adjective and noun from 1630s.