Aeschylus A.Ag 1444
ἄτιμα δ’ οὐκ ἐπραξάτην.
ὁ μὲν γὰρ οὕτως, ἡ δέ τοι κύκνου δίκην
τὸν ὕστατον μέλψασα θανάσιμον γόον
κεῖται, φιλήτωρ τοῦδ’· ἐμοὶ δ’ ἐπήγαγεν
εὐνῆς παροψώνημα τῆς ἐμῆς χλιδῆς.
The pair has met no undeserved fate. For he lies thus; while she, who, like a swan, 1445has sung her last lament in death, lies here, his beloved; but to me she has brought for my bed an added relish of delight.
LSJ adverb. in acc. δίκην, in the way of, after the manner of, c. gen., λύκοιο
κύκνου δίκη: in the manner of a swan singing ...
J.P. Harris says this is the earliest reference to the Swan Song which was picked up by the other Tragedians.
Cassandra’s Swan Song:
Aeschylus’ Use of Fable in Agamemnon
John Philip Harris
http://www.google.com/url?sa=t&rct=j&q= ... 0087,d.dmg