Dictionary.com's Word of the Year is...
metrical foot, late 14c., from Greek dactylos, literally "finger" (also "toe"), 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 dac·tyl (dāk'təl)
A finger or toe; digit.
metrical foot consisting of one long (classical verse) or stressed (English verse) syllable followed by two short, or unstressed, syllables. Probably the oldest and most common metre in classical verse is the dactylic hexameter, the metre of Homer's Iliad and Odyssey and of other ancient epics. Dactylic metres are fairly rare in English verse, one difficulty being that the prolonged use of the dactyl tends to distort normal word accent, giving the lines a jerky movement. They appeared with regularity only after poets like Robert Browning and Algernon Charles Swinburne successfully used the form in the 19th century. Dactylic rhythm produces a lilting movement as in the following example from Byron's Bride of Abydos: