Where did the idea of vampire invitation first originate?
It depends on what vampire literature you're reading.
Much literature decides to use this trope, but some do not. The reasons vary though.
Going back in various mythologies is the idea that supernatural beings
— such as vampires, ghosts, demons, witches, what have you — cannot
enter into a home unless invited to do so. Often such beings will try
to gain entrance by tricking a person into believing they are someone
Invitation is a weakness of vampires and hybrids, including Original
vampires/hybrids. In order to enter any house owned by humans,
witches, werewolves, or doppelgängers, vampires or hybrids must be
invited by the owners of the home. Once invited, the vampire cannot be
uninvited unless the ownership of the house changes.
In The Vampire Diaries, vampires were not created by the planet
compared to the other species. As a defense, nature attacks the
vampires with sunlight, wood, vervain, and other elements (for
example, water weakens vampires in the books). With the purpose to
defend against the undead, the living kept the vampires away by
banning them entry into their homes. Literally, it's like saying: I
invite my own death to my home.
How was Rebekah able to enter the Salvatore home
Entry to homes: Vampires cannot enter private human homes unless they
are invited in by the owner of the house. Vampires do not need to be
invited into public places (such as bars or restaurants). Humans can
rescind their invitations from vampires, which causes the vampire to
immediately leave the house. Vampires can get around this by
glamouring a person into inviting them in. Ancient vampires might not
be subjected to this weakness, suggested by Bill who drank Lillith's
whole remaining blood and Warlow that has never been invited to
Sookie's house.The death of the human owner of a residence allows any
vampire to enter even without an invitation.
Some traditions also hold that a vampire cannot enter a house unless
invited by the owner, although after the first invitation they can
come and go as they please. Though folkloric vampires were
believed to be more active at night, they were not generally
considered vulnerable to sunlight
The reasons being (from the sources):
- Protection for humans (that was contingent on their creation)
- It is sometimes not just for vampires, but for other supernatural creatures as well.
Then there are these other SFF.SE questions.
Could the Enterprise beam a vampire into a house she didn’t have permission to enter? [closed]
If a vampire would stand inside a house when it was built would he be albe to leave? [closed]
Is there any down side to being a vampire in modern fiction? [closed]
How did Silas get inside Caroline's house?