The verse beginning "in the female prison" can surely be nothing other than sexual symbolism?

The Royal Canal is simply the Royal Canal. Behan was born at 14 Russell Street, Dublin, between the North Circular Road and the Royal Canal. He played on its banks and learned to swim in its waters. It was important to him. (And to his brother Dominic, whose ashes were scattered in the Royal Canal). Mountjoy Prison is also on the Canal's banks and would have been visible from inside. The sight of it stretching away in the distance would,for Behan, have been a particularly poignant sight.

The Quare Fellow was inspired by the execution of the real life Barney Kirwan on 2 June 1943 (while Behan was inside) for the murder of his brother in a dispute over the inheritance of the family farm. He then skinned the body and buried it in a bog. Behan thought him "bloody gentle", but also, "a complete nut".

"The metal triangle used to be rung to call the prisoners to their tasks" - Kathleen Behan, Brendan's mother.