Abdullah ibn Rafi’ reported: I said to Abu Huraira, may Allah be pleased with him, “Why were you nicknamed Abu Huraira?” Abu Huraira said, “I would tend to the sheep of my people, and I had a small kitten. I used to place it in a tree at night, and during the day, I would take it and play with it. So they nicknamed me Abu Huraira, ‘father of the kitten.’”
Source: Sunan al-Tirmidhī 3840
Grade: Hasan (fair) according to Al-Tirmidhi
عَنْ عَبْدِ اللَّهِ بْنِ رَافِعٍ قَالَ قُلْتُ لِأَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ لِمَ كُنِّيتَ أَبَا هُرَيْرَةَ قَالَ كُنْتُ أَرْعَى غَنَمَ أَهْلِي وَكَانَتْ لِي هُرَيْرَةٌ صَغِيرَةٌ فَكُنْتُ أَضَعُهَا بِاللَّيْلِ فِي شَجَرَةٍ فَإِذَا كَانَ النَّهَارُ ذَهَبْتُ بِهَا مَعِي فَلَعِبْتُ بِهَا فَكَنَّوْنِي أَبَا هُرَيْرَةَ
3840 سنن الترمذي كتاب المناقب باب مناقب أبي هريرة رضي الله عنه
6/156 المحدث الترمذي خلاصة حكم المحدث حسن غريب في سنن الترمذي