The word πεμπώβολα ‘having five prongs’ at Iliad Ι 463 belongs to the dialect family known as Aeolic, as distinct from the "default" language of Homeric poetry, which belongs to the dialect family known as Ionic. The part of this compound adjective that means ‘five’ is Aeolic πέμπε, to be contrasted with Ionic πέντε. In Aeolic, kʷ becomes π before ε, whereas it becοmes τ before ε in Ionic. Further commentary on pp. 173-175 of Nagy 2011, "The Aeolic Component of Homeric Diction,"
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In that article, I cite an interesting remark in the “pseudo-Herodotean” Life of Homer, Vita 1.517–537. Toward the end of this passage, the author says: 'You see, the Aeolians are the only ones among the Greeks who roast the innards with forks that have five prongs [πεμπώβολα], while the other Greeks use forks that have three prongs. And of course the word that the Aeolians use for ‘five’ [pente] is pempe.'