Mayasura (मयासुर) who was the architect of demons gave Bheem his gadha and Arjun his sankha named as Devadatta (देवदत्त)
It is mentioned in Mahabharata – Sabha Parva – Chapter 3, Mayasura as a mark of devotion towards pandavas brought this gadha (mace) and Devadatta sankha from the kingdom of King Vrishaparva (वृषपर्वा) where these were kept.
सा वै शतसहस्रस्य सम्मिता शत्रुघातिनी।
That mace who destroys the enemies and is equivalent to one lakh mace.
वारुणश्च महाशङ्खो देवदत्तः सुघोषवान्।
सर्वमेतत्प्रदास्यामि भवते नात्र संशयः।।
There is also conch shell of god Varuna named as Devadatta, who has great sound. Let me bring those and offer to you.
गदां च भीमसेनाय प्रवरां प्रददौ तदा।
देवदत्तं चार्जुनाय शङ्खप्रवरमुत्तमम्।।
He than offered that great mace to bheemsen and conch shell named Devadatta to arjuna.