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Ἀχαιοί

Μολὼν λαβέ -> Come and take them
Plutarch, Apophthegmata Laconica 225C12

English (Autenrieth)

the Achaeans, the chief tribe of Greeks in Thessaly, Messēne, Argos, and Ithaca; mostly as a collective appellation of the Greeks before Troy, Il. 1.2, etc.; epithets, ἀρηίφιλοι, δῖοι, ἑλίκωπες, ἐυκνήμῖδες, κάρη κομόωντες, μεγάθῦμοι, μένεα πνείοντες, χαλκοχίτωνες.

Russian (Dvoretsky)

Ἀχαιοί: οἱ ахейцы или ахеяне, т. е. жители Ахеи Пелопоннесской или Фессалийской, перен. греки (в отличие от троянцев) Hom., Hes., Trag., Her., Xen., Plat., Arst., Plut.

Etymological

Grammatical information: pl. m.
Meaning: name of a Greek tribe (Il.).
Other forms: sg. Ἀχαιός Achaean, f. Ἀχαιαί, sg. (s. Schwyzer 460).
Derivatives: Ἀχαιΐς, -ίδος f. the land of the A. (sc. γαῖα) or the Achaean f. (sc. γυνή), also Ἀχαιϊάς f. (Il.); Ἀχαιϊκός, Att. Ἀχαϊκός (cf. Schwyzer 265f.) Achaean; Ἀχαιΐη, Att. Ἀχαΐα f. a Thessalian and Peloponnesian region Achaia; also a town (Rhodos etc.), perhaps trisyllabic, s. below.
Origin: PG [a word of Pre-Greek origin]
Etymology: The name Ἀχαιοί < ἈχαιϜοί (cf. Lat. Achīvī) is known from Egyptian sources as qjwš', read as Aqaiwaša. Also in Hitt. Aḫḫiya, later Ah̯h̯iyawā, from *ἈχαιϜία or *ἈχαίϜα(?); Kretschmer Glotta 21, 227). Against this Sommer (Aḫḫijavā-Urk., A. u. Sprw., IF 55, 169ff.). The equation is now generally accepted, but the Hittite form has not been satisfactorily explained. (Worthless Finkelberg, Glotta 66, 1988, 127 - 134, who derives the Greek form from Hitt. Ah̯h̯iyawa (!), with h₂y > χ.) - The name is no doubt a Pre-Greek name (Akayʷa?). On the historical side Lehmann, Historische Zeitschr. 262, 1996, 1 - 38; Niemeyer Aegaeun 19, 1999, 141 - 155.