ἡ αἴξ, αἰγός – a (she-) goat
ὡς τὸ πρόβατον καὶ ἡ αἴξ ἥμερόν ἐστι ζῷον· τίς δ’ ἐστὶν ἡ φωνὴ τῶν αἰγῶν; ἑλληνιστὶ αἱ αἶγες μηκῶνται, ὃθεν λέγει ἤδη ὁ Ὅμηερος·
οἵ τέ σε πεφρίκασι λέονθ᾽ ὡς μηκάδες αἶγες.

Like the sheep a goat is a tame/domesticated animal, too. What is the sound that goats make? In Greek the goats bleat, whence already Homer says:
They shudder at you like the bleating goats at the lion. (Ilias 11.383)
(All images in this series are under the Creative Commons License: Feel free to share! 🙂 )