出典:Wiktionary
The second pronunciation (with a long "a" sound) is derogatory and used only in the sense of a person.
From Ancient Greek Ἄραψ (Áraps, “Arab”), from Arabic عَرَب (ʿarab).
any Arab
street arabs
the Arabic figures
the Arabic numerals
the Saudi-Arabian desert
the Arabian desert
唐草模様で.