dactyl (n.)youdaoicibaDictYouDict[dactyl 词源字典]
metrical foot, late 14c., from Greek dactylos, literally "finger" (also "toe"), which is of unknown origin; the metrical use (a long syllable followed by two short ones) is by analogy with the three joints of a finger.[dactyl etymology, dactyl origin, 英语词源]