What does "Merlin's beard!" mean?

I know that Merlin's beard! is an exclamation from Harry Potter which is similar to "Oh Lord!". and it is a common wizarding expression used to show surprise. Can we use it this expression in the muggle world?

I just wanted to know whether it is a proper exclamation which has its own origin and what is the literal meaning of this?

Are there any other exclamations like this?

This expression is completely fictional. In the Harry Potter books, there are other 'wizarding idioms' that sometimes paraphrase ones existing in the real world. A (presumably, incomplete) list can be found here.

It is perfectly acceptable to use them in the Harry Potter fandom. Certain expressions from the books are well-known to this community, and you won't raise any eyebrows by saying "Would you care for a lemon drop?", "Expelliarmus!" or "Constant vigilance!" even in a seemingly unrelated situation.

You can easily remember similar expressions from other books or movies: "May the Force be with you!" from the Star Wars, "I'll be back" from the Terminator. Still, you cannot assume that every speaker of English knows each one of these (keeping in mind the amount of available books, movies, cartoons and comics).

So, my conclusion is that "Merlin's beard" can certainly be used as a personal catch phrase in the Muggle world. Just don't expect everyone to recognise it.

It's unique to Harry Potter, similar to Robin saying, "Holy [relevant object], Batman!" It's meant to show Merlin as sort of wizard replacement, in colloquialisms, for St. Pete, Jesus, or similar -- just a small thing to augment the presentation of the wizarding culture, which Rowling does in so many places throughout the series. After all, the isolated wizard community would likely have different colloquialisms, different references/allusions to make, and different ways to express irreverence than we muggles have.

I don't think it would hurt for a muggle to use the phrase, though. :]

That is probably a reference to the archaic exclamation "By Odin's Beard!", which was (supposedly) originally a formal oath, but came to be just a profane (and later a substitue profane) oath. Something you might reflexively shout after hitting your thumb with a hammer.

An author at Urban Dictionary claims it was actually an oath to not shave until something is accomplished, but I'm not sure I buy that.

Rowling seems to be fond of building her own semi-parallel universe for Wizards in the HP books. This is sort of her way of saying that the "Wizarding world" views Merlin in the same mythic way that normal Anglo-Saxon folk might view Odin.