An opportunity to make a pun—itself a pun on "opening", except with "pun" included. Not to be confused with "O'punning", the act of punning in Gaelic.
Q: Was this an intentional pun or one that just happened?
A: Maybe it just happuned but I wouldn't put it past him to have seen an opuning and gone for it. Me, I'd never do anything like that.