Pennywise does live in the sewer, rent free. That speaks to financial discipline. And he eats children, who are also free. Based on that, I'm gonna say the name is more likely earnest than ironic.
There is a guy here at work that calls me "Chief." There's another guy here at work that calls me "Pardner." I'm beginning to feel like I'm a double-agent in a clandestine Cowboys and Indians war.