The hidden blades aren’t. We’ve actually talked about the Assassin’s Creed franchise a few times before. The basic idea of shiving a guy, and then palming the knife and walking off? Yeah. That works. The idea of strapping said blade to your arm? Not so much.
Especially not in Renaissance Italy, when people would conceal daggers on their forearms, and handshakes were specifically used to make sure the person you were meeting wasn’t about to perforate your kidney.
The phrase, “a knife up your sleeve” used to be a lot more literal.
The biggest problem with Wolverine’s claws is… where the hell does he keep them? They’re substantially longer than his hands, so they need to start in his forearms, and then extend through his wrists, which means his wrist needs to be perfectly aligned when he tries to extend them. It also opens the question to, “how do these stay in place while extended?” Structurally, that’s more weight than the bones in your hand are designed to support, so either his hands would need to be substantially different, physiologically, or it’s running on Chris Claremont logic.
That said, both of these designs get at weapons that are, more or less, real. Punch daggers are weapons where the grip is set, perpendicularly, behind the blade. They’re designed to be held in a closed fist, with the blade protruding between the middle and ring finger (though other configurations exist). They can deliver more force on impact than a common knife design. The most famous example of this design is probably the katar from India.
These are not normally attached, directly to the wrist, but allow similar strike patterns while offering slightly more flexibility in their use.
In the case of Wolverine, his claws somewhat resemble the Bagh Naka (or “tiger claws”) which also originates from India. This consists of several hooked claws mounted on a bar which is held in the hand, while the blades protrude between the fingers (or, with some designs, from the palm). In some circumstances this would appear like a much shorter, curved, version of wolverine’s claws. These are used to support several hand to hand techniques that involve raking the opponent with the blades.