FROM STRONG’S GREEK DICTIONARY (1890)

Strong’s Greek Dictionary (1890) — public domain, printed whole.

pou ποῦ — poo — genitive case of an interrogative pronoun pos (what) otherwise obsolete (perhaps the same as 4225 used with the rising slide of inquiry); as adverb of place; at (by implication, to) what locality:--where, whither.

see GREEK for 4225