Liddell-Scott-Jones

καθαρεύω (kathareuō) be clean ^G:V

καθαρεύω-εύω,

(καθαρός) to be clean or pure, [Refs 5th c.BC+]; of sifted grain, [Refs 3rd c.BC+]: with genitive, to be clean or free from, φόνου [Refs 5th c.BC+]; [κακιῶν] [Refs 1st c.BC+]; κ. πυρετοῦ to be free from fever, [Refs 2nd c.AD+]; κ. ἀπ᾽ αὐτοῦ (i.e. τοῦ σώματος) [Refs 5th c.BC+]; κ. γνώμῃ to be pure or clean in mind, [Refs 5th c.BC+]

__2 Rhet., of a writer, to be pure, correct in language, κ. τὴν διάλεκτον [Refs 1st c.BC+]; οἱ καθαρεύοντες purists, [Refs]
__3 Grammars, to be preceded by a vowel, to be 'pure' [Refs 2nd c.AD+]; contain a 'pure' syllable, Hdn.Gr.[Refs]