Note 32 — Chapter V · CAMPAIGN OF KHALID AGAINST THE FALSE PROPHET TOLEIHA. A.H. XI. Nov. A.D. 632.
Reading edition
Abu Bekr means ‘Father of the young camel,’ and they called him by the nickname Ab ul Fasîl, ‘Father of the foal.’ Adî answered, ‘He is not Ab ul Fasîl, but, if you like it, Ab ul Fahl,’ ‘Father of the stallion,’ i.e. endowed with power and vigour.
In the Persian version of Tabari, the surname is by a mistake given as Ab ul Fadhl, ‘the Father of Excellence,’ and is applied to Khâlid.