The Collaborative International Dictionary of English v.0.48:

paeon \p[ae]"on\ (p[=e]"[o^]n), n. [L. paeon, Gr. paiw`n a
   solemn song, also, a p[ae]on, equiv. to paia`n. See
   P[ae]an.] (Anc. Poet.)
   A foot of four syllables, one long and three short, admitting
   of four combinations, according to the place of the long
   syllable. [Written also, less correctly, p[ae]an.]
   [1913 Webster]