Nope, not a dog’s name at all - though if you want to name your dog [name_u]Rex[/name_u] or [name_u]Max[/name_u] or [name_m]Steve[/name_m], hey, free country. But it is by no means exclusively a dog’s name. Perfectly acceptable for a human.
I’m familiar with it but I don’t particularly like it. T-[name_u]Rex[/name_u] association. The boy a year below me named [name_u]Rex[/name_u] always got called Jurassic [name_m]Park[/name_m] and JP once kids were old enough to make the connection. I always felt bad for him in school because his parents named him after a dinosaur.
It might work. But it reminds me of a Far Side comic with a dog praying by the bedside (“and please let Mom, Dad, [name_u]Rex[/name_u], [name_f]Ginger[/name_f], [name_m]Tucker[/name_m], me, and all the rest of the family see color.”) [name_u]Gary[/name_u] [name_m]Larson[/name_m] did have plenty of pets with human-ish names in his comics, though.
I don’t really associate the name [name_u]Rex[/name_u] with a dog or a dinosaur. Never met a dog called [name_u]Rex[/name_u] or [name_u]Max[/name_u] or Sparky… The only dogs I know are called [name_f]Lucy[/name_f], [name_f]Joline[/name_f], [name_u]Sam[/name_u], [name_m]Mungo[/name_m], [name_u]Hunter[/name_u] and [name_m]Pablo[/name_m].
I associate [name_u]Rex[/name_u] more with it’s actual meaning, which is [name_m]King[/name_m].
Also, little boys are always emulating superheroes and pretending to be Batman or fantasy characters. Can’t help but think that T-[name_u]Rex[/name_u] is actually a pretty fun alter ego for an adventurous, imaginative little boy.
I think it’s a daring choice, but I like it. If you like it but have concerns about it, I think it works well as a nickname for [name_m]Regis[/name_m] (too [name_m]Philbin[/name_m]?) or [name_m]Reginald[/name_m].
I don’t think [name_u]Rex[/name_u] is too out there at all, and I am fairly conservative and like names that are classic but not overused. I think [name_u]Rex[/name_u] is just a little different version of [name_u]Max[/name_u], or at least it has a similar ring. I like it! Go for it.
I think I’d like it better as a nn. Maybe for [name_m]Reginald[/name_m], [name_m]Reuben[/name_m], [name_m]Remington[/name_m], [name_m]Redmond[/name_m], Rickman, or [name_u]Reynold[/name_u].
Seems very tight as the only option.
I like it, but I’m quite fond of the mystery author [name_u]Rex[/name_u] Stout, and association with him in my mind gives it a rather dapper [name_m]Art[/name_m] Deco feel.
He was born in 1886 and wrote the [name_m]Nero[/name_m] [name_m]Wolfe[/name_m] mysteries in the '30s. I picture novels full of fedoras, gin, and smooth men who light cigarettes for ladies. [name_u]Rex[/name_u] is cool by me, but very overtly retro feeling.