anapest (n.)

also anapaest, "two short or unaccented syllables followed by a long or accented one," 1670s, from Latin anapaestus, from Greek anapaistos "struck back, rebounding," as a noun "an anapest," verbal adjective from anapaiein "to strike back," from ana- "back" (see ana-) + paiein "to strike" (from PIE root *pau- (2) "to cut, strike, stamp"). So called because it is a dactyl reversed.