Agiyaras in Jyaistha month is also known as Bhim Agiyaras. Why is the name of Bhim mentioned? any story of mango eating in Bhim Agiyaras?
Nirjala Ekadashi is also known as Bhimseni or Bhima Ekadashi due to one legend associated with Nirjala Ekadashi.
Bhimsen, the voracious eater, was not able to control his desire of having food. Due to this reason he was not able to observe Ekadashi fasting and met Maharishi Vyasa to find some solution.
Sage Vyasa advised Bhima to observe single Nirjala Ekadasi fasting to compensate for not observing all Ekadashi fasting in a year. ~nirjala-ekadashi-drikpanchang
Due to this legend Nirjala Ekadashi is also known as Bhimseni Ekadashi.
The more detailed story is given here (in Hindi) and in PADMA-PURANA : UTTARAKHANDA : Chapter 51. Nirjala Ekadasi.