In Sanskrit, Arindam means a man who has won over all his enemies.
In Hindu mythology, the tragic hero Indrajit, son of King of Lanka, Ravana, got this title "Arindam" after he conquered his enemies. In Eastern part of India mainly Bengal, Arindam is quite a popular name amongst the Bengalis. In Bengali, it is pronounced as "O-Reen-Dom" .
Interestingly, Arindam is also a name of Lord Shiva (Maheshwara, a hindu god).