Early 19th century; earliest use found in The Quarterly Review. From penta- + syllable, after post-classical Latin pentasyllabum, use as noun of neuter of pentasyllabus.
Definition of pentasyllable in US English:
pentasyllable
noun
A word with five syllables.
Origin
Early 19th century; earliest use found in The Quarterly Review. From penta- + syllable, after post-classical Latin pentasyllabum, use as noun of neuter of pentasyllabus.