A similar word, πορτοκαλί, occurs in Greek (per My Big Fat Greek Wedding 
). I suspect Arabic actually borrowed this word from Greek.
It’s possible, but my first thought is that Greek acquired the word in the same way I imagine Bulgarian did - from Turkish. Like Bulgaria, Greece was part of the Ottoman Empire for hundreds of years and Greek has plenty of Turkish borrow words.
It’d probably take a professional etymologist to figure out in exactly which direction the word traveled.