Acts cites Psalm 131.11, but the LXX has κοιλία not the term ὀσφῦς. Irenaeus comments on Psalm 131.11 that it must be the womb of woman, since Jesus was born not of a David’s loins from the belly of the virgin Mary (haer. 3.21.5; ANF 1[sic]):
And when He says, “Hear, O house of David,” He performed the part of one indicating that He whom God promised David that He would raise up from the fruit of his belly (ventris) an eternal King, is the same who was born of the Virgin, herself of the lineage of David. For on this account also, He promised that the King should be “of the fruit of his belly,” which was the appropriate [term to use with respect] to a virgin conceiving, and not “of the fruit of his loins,” nor “of the fruit of his reins,” which expression is appropriate to a generating man, and a woman conceiving by a man.
Irenaeus here discusses Psalm 131.11 without regard to Acts, since he contradicts Luke on this point. If it is possible for Irenaeus to know the expression “fruit of the belly” and “fruit of loins” without reference to Acts, it is likewise possible for the author of the Acts of Paul, to use the term without knowing Acts, contra Julian Hills, Semeia 80 (1997) 152f. Furthermore, it is not excluded that a copy of the LXX available to both Luke and the author of the Acts of Paul had this variant reading. H. Seesemann writes (s.v. ὀσφῦς,TDNT 5.497): “From Ac. 2:30 ὀσφύος came into the LXX Codex R saec VI.” Is this possibly a genuine variant that Luke knew? Perhaps someone out there in the blog world knows the answer to this question.