gatekeeper

Etymology

From gate + keeper.

noun

1. A person or group who controls access to something or somebody.
   The sources the citations are drawn from are significant, being printed books or newspapers subject to editorial processes and gatekeepers of language standards, as opposed to unedited texts such as blogs, chatroom logs or student writing. 2012, James Lambert, “Beyond Hobson-Jobson: A new lexicography for Indian English”, in World Englishes, page 302
2. A person who guards or monitors passage through a gate.
   At each station is a level crossing, in addition to others away from stations, and, as both the road and rail traffic are heavy, the gatekeepers (mostly signalmen) are quite busy and have acquired well-merited mention for reducing delays to road traffic to a minimum. 1946 January and February, G. A. Sekon, “The L.B.S.C.R. West Coast Section”, in Railway Magazine, page 15
3. A common orange and brown butterfly with eyespots, Pyronia tithonus, of the family Nymphalidae.
4. (psychology) In dissociative identity disorder, an aspect of the personality that controls access to the various identities.
5. One who gatekeeps.