Genitive case of an indefinite pronoun pos (some) otherwise obsolete (compare posos); as adverb of place, somewhere, i.e. Nearly -- about, a certain place.
see GREEK posos
STRONGS NT 4225: πούπού, an enclitic particle, from Homer down;
1. somewhere: Hebrews 2:6; Hebrews 4:4.
2. it has a limiting force, nearly; with numerals somewhere about, about (Herodotus 1,119; 7, 22; Pausanias, 8, 11, 2; Herodian, 7, 5, 3 (2 edition, Bekker); Aelian v. h. 13, 4; others): Romans 4:19.