His father held the cognom 'Strabo,' which means 'cross eyed' (Pothecary,1999). As his father was a relative new comer to the higher tiers of the gens Pompeia, they may not yet have acquired a particular familia epithet/cognom, and held them in the traditional sense of being named for a characteristic or deed. I would assert that he did not take up the name of Strabo, and he acquired 'Magnus' at a relatively young age (Plutarch, Pompey) as his only cognom.