a rare beautiful day in toronto!

Doesn't "hoary" also mean bravery or full of beans or whatever?

We used to sing "Men of Fenwick, young and hoary....". back in grade school.

Of course we changed the words to "young and horny". Because we were poets and immature.

Fenwick?

I don't know the song you're referring to, so I'm missing out on most of the context. From what you've provided, I'd suspect it's referring to Grey-Haired. (I've heard it used that way more than once.) The meaning the line you quoted would then be "young & old".

Brian