LSJ
Ion. κου, Aeol. ποι Sappho Supp. 25.17, Pi. P. 5.101, BCH 37.157 (Cyme, iii BC), prob. in Alc. 9; — enclit. Adv. anywhere, somewhere, Il. 16.514, etc. ; freq. with other Advs. of Place, οὐχ ἑκάς π.
somewhere not far off, S. Ph. 41; πέλας π. ib. 163 (anap.); μηδαμοῦ… π. ib. 256 (dub.l.); π. πέραν τοῦ ποταμοῦ X. An. 4.3.3; ἄλλοθί π. D. 4.41; τῇδέ π. Plb. 3.108.3, etc. ; c. gen., ἀλλά π. αὐτοῦ ἀγρῶν in some part there of the fields, Od. 4.639; ἐμβαλεῖν π. (fort. ποι) τῆς χώρας some part of the country, X. Cyr. 6.1.42; εἴ π. τῆς χώρας ταὐτὸ τοῦτο πάθος συνέβη D. 18.195. without reference to Place, in some degree, καί πού τι Th. 2.87; freq. to qualify an expression, perhaps, I suppose, Hom., etc. ; added to introductory Particles, οὕτω π.… Il. 2.116; Ζεὺς μέν π. τό γε οἶδε 3.308; ὡς ὅτε π. 11.292; ἤν π., εἰ μή π., X. Hier. 3.2, Pl. R. 372a; strengthd., τάχ’ ἄν π. S. OT 1116; ἴσως π. E. El. 518; attached to single words to limit their significance, πάντως κ. Hdt. 3.73; τί π. δράσεις· what in the world? A. Pr. 743; οὐδείς π. Pl. Phlb. 64d; with numerals, ἔτεα τρία καὶ δέκα κ. μάλιστα about thirteen years, Hdt. 1.119, cf. 209, 7.22, etc. ; οὔ τί που denies with indignation or wonder, surely it cannot be…, οὔ τί π. οὗτος Ἀπόλλων Pi. P. 4.87, cf. S. Ph. 1233, Ar. Nu. 1260, Pax 1211, Ra. 522, Pl. R. 362d, etc. ; οὐ δήπου adds a shade of suspicion, οὐ δήπου Στράτων· Ar. Ach. 122, cf. Av. 269, Pl. Smp. 194b; for δήπου, ἦπου, v. sub vocc. — In late writers (LXX Jo. 2.5, al., Ev. Jo. 7.35, al., Arr. Epict. 1.27.9, 4.1.93, etc.) ποῦ, που take the place of ποῖ, ποι, with Verbs of motion, as in Engl.
where for whither? This idiom (condemned by Phryn. 30, ποῦ ἄπει… ἁμάρτημα) is found occasionally in early authors, ποῦ τοι ἀπειλαὶ οἴχονται; Il. 13.219; ἐξελθών που Antipho 2.4.8; ἰόντα που X. Cyr. 1.2.16; but in pure Att. only as f.l. for ποῖ, ποι.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)