Wikipedia tells me that Arabic is only about 2000 years old. If Job’s daughters had Arabic sounding names, that does not mean that Job was an Ishmaelite.
Arabic as we know it today may only be 2.000 years old, but the base language is much older.
We know from the text itself that he was a righteous gentile from what is now Saudi Arabia, which makes him either an Ishmaelite or less likely from the line of Esau, more likely Ishmaelite.
Given his daughters’ names were Proto-Arabic, the consensus is Ishmaelite.