Loan word, probably from Demotic yb (“ivory, Elephantine”), from Egyptian Ab-b-w-E26 (ꜣbw, “ivory, elephant, Elephantine”). Compare Coptic ⲓⲏⲃ (iēb, “Elephantine”); also note Sanskrit इभ (íbha) and Tigre ኣቦት (ʾabot).
In any case, probably cognate with the second half of Ancient Greek ἐλέφας (eléphas, “elephant”)