"metrical foot consisting of two long syllables," late 14c., from Old French spondee (14c.), from Latin spondeus, from Greek spondeios (pous), the name of the meter originally used in chants accompanying libations, from spondē "solemn libation, a drink-offering," related to spendein "make a drink offering," from PIE root *spend- "to make an offering, perform a rite," hence "to engage oneself by a ritual act" (source also of Latin spondere "to engage oneself, promise," Hittite shipantahhi "I pour out a libation, I sacrifice"). Related: Spondaic.
And [the spondee] has the perpetual authority of correspondence with the deliberate pace of Man, and expression of his noblest animal character in erect and thoughtful motion : all the rhythmic art of poetry having thus primary regard to the great human noblesse of walking on feet ; and by no means referring itself to any other manner of progress by help either of stilts or steam. [John Ruskin, "Elements of English Prosody, for use in St. George's Schools," 1880]