The Greek of Rom 1:14 is:
Ἕλλησίν τε καὶ Βαρβάροις, σοφοῖς τε καὶ ἀνοήτοις ὀφειλέτης εἰμί·
I would translate this rather literally as:
Both to Greeks and to Barbarians; to wise and to foolish, I am a debtor.
Concerning the operative word here: Βαρβάροις = barbarians (literally) is a pejorative term for non-Greeks. According to Thayer:
properly, one whose speech is rude, rough, harsh, as if repeating the
syllables βαρβαρ (cf. Strabo 14, 2, 28, p. 662; ὠνοματοπεποίηται ἡ
λέξις, Etym. Magn. (188, 11 (but Gaisf. reads βραγχός for βάρβαρος);
cf. Curtius, § 394; Vanicek, p. 561)); hence, ... The Greeks used
βάρβαρος of any foreigner ignorant of the Greek language and the Greek
culture, whether mental or moral ...
Hence the various Bible versions are divided between "barbarians" and "non-Greeks", except YLT which has "foreigners" (rather interpretive for Young!)
Paul here uses a very common literary device called a hendiadys, which employs two opposites to mean "everything" in some sense. Such a very common in most languages; for example, in English we have: Day and night = continually, all the time; Searched high and low = searched everywhere; Time and again = repeatedly; Neither one nor the other = nothing; Turn neither to the right nor the left = do not deviate from the current path; For better or worse = under all circumstances, etc, etc.
In Rom 1:14 Paul uses a hendiadys twice:
- Greeks and non-Greeks (ie everyone)
- Wise and foolish (ie, everyone)
Thus, Paul affirms that he is a debtor to everyone, all people, twice!