Eel weirs were a common feature of Irish rivers for centuries, designed to funnel the movement of eels, which were a significant food source and a tradeable commodity, particularly for monastic communities and their tenants. The name here hints at a long history of catching eels at this particular bend of the west-to-east flowing Boyle River, even if nothing visible survives to confirm it.

A documentary reference places a weir somewhere in this stretch of the river as early as 1583 to 1584, suggesting the site had been in active use long before the Victorian-era structure that stands today. That earlier weir, along with any others that had accumulated over the centuries, was cleared away in 1848 when the Commissioners for the Improvement of the Navigation of the River Shannon undertook their works. The Commissioners were a body established to regularise and deepen the Shannon system for commercial river traffic, and their programme frequently involved removing or remodelling older obstructions that interfered with navigation. The weir that replaced whatever preceded it was built to their specifications, leaving no visible trace of the earlier structure or structures beneath or beside it.