γοῦν (postpositive; first in Aeschylus) is a restrictive particle from γέ οὖν. Its meaning varies according to the prominence of the γέ or οὖν; often certainly, at any rate (
ἔτι γὰρ οὗτοι κακί_ονές εἰσι τῶν ὑφ' ἡμῶν ἡττημένων· ἔφευγον γοῦν πρὸς ἐκείνους καταλιπόντες ἡμᾶς
γοῦν may emphasize a pronoun; as πρὸς γοῦν ἐμοῦ
In answers γοῦν means
γοῦν finds the proof of an assertion in one of several possible facts or occurrences; γάρ gives the reason in general, but gives no particular instance; δ' οὖν has an adversative force: ‘be that as it may, yet at any rate.’
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].