Narrated 'Abdullah bin Rafi':
"I said to Abu Hurairah: 'Why were you given the Kunyah Abu Hurairah?' He said: 'Do you not fear me?'" He said: "Indeed, I am in awe of you.' He said: 'I used to tend the sheep of my people, and I had a small kitten; so I used to place it in a tree at night, and during the day I would take it and play with it. So they named me Abu Hurairah.'" (ES)
English reference (ES): Vol. 1, Book 46, Hadith 3840 (ES)
Arabic reference (ES): Book 49, Hadith 4211 (ES)