Lewis & Short

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Aesernĭa (Es-), ae, f., a town in Samnium, on the river Vulturnus, now Isernia, Cic. Att. 8, 11, D, § 2; Vell. 1, 14; Liv. Epit. 72, 73 al.
Hence, Aesernīnus, a, um, adj. pertaining to or a native of, Æsernia: ager, Liv. 10, 31: turma, id. 44, 40.
Also a surname of M. Marcellus, who was taken prisoner there by the Samnites, Liv. Epit. 73; Plin. 12, 1, 5, § 12.
Aesernīni, ōrum, m., the inhabitants of Æsernia, Liv. 27, 10.
Aeserninus was also the name of a renowned gladiator; hence the proverb: Aeserninus cum Pacidiano, one champion against another, when two equally great men are compared together or engaged in mutual conflict, Lucil. ap. Non. 393, 28; Cic. Q. Fr. 3, 4; id. Opt. Gen. Orat. 6 (cf.: cum Bitho Bacchius, Hor. S. 1, 7, 20).