Why Indra is called as Shatakratu ( शतक्रतु ) ?
As mentioned in Mahabharata Shantiparva Chapter 33 verse 39
मरुद्भिः सह जित्वारीन् भगवान् पाकशासनः ।
एकैकं क्रतुमाहृत्य शतकृत्वः शतक्रतुः ।।
“Lord Paksan Indra after defeating his enemies along with Marutas ( मरुद् गण ), performed hundred Ashvamedha yagna, one after another and due to this he become famous as Shatakratu ( शतक्रतु )”
Shatakratu ( शतक्रतु ) – The one who has performed 100 (शत) yagna’s ( क्रतु)
