Fannyish

To act or behave in a childish or absurd manner. (Generally relates to someone stuck up their own arse)

I couldnt believe how fannyish Jamie was acting today again, he's a tool!

fannyishness

a)To perpetually behave in an absurd manner, ie. to act like a fanny .So much so , that it becomes a way of life …expected if you like ….

b)the art of displaying fannyish behaviour

“ See Robert , I wonder if he could be cured of his fannyishness …. I can’t bear to been seen in public with him “