I always thought it was 'Heeeyyy' - a longer, cooler version of saying 'Hey!'
Incidentally - this just confirms that those of us answering this thread are old farts! I don't think any of the fine young ladies advertising on this site have even heard of 'Happy Days'!
But no one was cooler than the Fonz back then.
"Don't be reckless with other people’s hearts. Don't put up with people who are reckless with yours"
Sorry for this thread guys. It seemed important when I started it. Truth is I walked in on two naked snails doin it today and I haven't been right since.
I saw an interview once with Henry Winkler and he said that he got the ayyy and wooo (don't know the spelling of that one) from his favourite past time, horse riding!!!! Not as cool any more.
Also, there was another of his quotes or actions that he claimed he took from fly fishing