[name]Just[/name] remembered this name - I knew a [name]Fernando[/name] in high school who went by [name]Fern[/name]. I thought it had both a nature and historical appeal 
Also makes me think adventurous, explorer!
I know a [name]Fernanda[/name] who goes by Fer, but I think it works wonderfully for boys ([name]Fernando[/name]) too.
Personally, although I have some good associations with [name]Fernando[/name] and Fernandez, I wouldn’t use them. A lot of people (in my area, also football fans) tend to shorten [name]Fernando[/name] to [name]Nando[/name], which I really don’t like.
I’d use [name]Fernando[/name]. Fernandez is the surname, meaning “son of [name]Fernando[/name]”. But [name]Fern[/name] makes a nice nickname for either. I also like [name]Fernanda[/name] for a girl.
I have a grandfather [name]Fernando[/name] and an aunt [name]Fernanda[/name]. I would use it because it has personal meaning to me, but I would use them regardless. I think [name]Fern[/name] is a nice NN.
[name]Fernando[/name]'s pretty dated and while I do like some dated names (like [name]Feliciano[/name]), [name]Fernando[/name] isn’t one I like much… I do like the nickname Fer, sort of. I know a number of Fernandos, it’s a fine name, just I like a ton of other Spanish names a lot more. [name]Fern[/name] is kind of weird to me, though. I mean, I like [name]Fern[/name] a lot on a girl, but I’m not in to it on a boy.
Fernandez is a last name to me, and I don’t like the sound of it either, so I definitely wouldn’t use it.
It is not my current style, but one thing I am learning when it comes to names is never say never