I'm pretty vague about this, but it has been my impression that
Mara is a Hebrew name meaning Bitterness. It depends, perhaps, on how close
Mara is to
Miriam - who is a character who features in Exodus and may well have had an Egyptian name quite naturally.
Problems arise with names - any old words, actually - in languages where the vowels are omitted in writing. Several millennia later, it's often anyone's guess where and what they would have been.