Frederick, what a great name! Would you mind posting the middle name, too? Just curious what it is.
Henry (Harry, Hal, Hank)
I'm not sure that any of these are what you were going for, but hopefully I was on the right track! Good luck with your naming!
EDIT: David is a quite nice name! And it goes well with Frederick. Frederick David. Do you want the same pattern for your second son--longer/old-fashioned and then shorter/classic?
Myself. Although if you go to nameberry.com, it is phenomenal! Behindthename.com, too, or nymbler.com, if you want to expand your list. And "You Can't Call It 'It'" is always worth a look. (: