I love words and language, and I was initially puzzled by the expression 'wissenhall'/ 'wizzenhall'.
This morning I had a thought. Perhaps it should be written 'wise and all'. I can almost hear some of my relatives add 'and all' to an adjective. These are folk who would speak using what is now termed Ulster Scots dialect.
For instance, 'he was wise and all, but he never made much money...'; 'she was helpful and all, and we soon found our way again'. Of course in Ulster Scots it would sound more like "wise 'n all".
What does it add to the meaning? Possibly a slight emphasis of the adjective. It's probably a stylistic thing too.
I hope this helps.