librarian

noun

1. a person trained in library science and engaged in library service.
2. a person in charge of a library, especially the chief administrative officer of a library.
3. a person who is in charge of any specialized body of literature, as a collection of musical scores.

noun

1. a person in charge of or assisting in a library

n.“custodian of a library,” 1713; see library + -an. Earlier form was library-keeper (1640s), and librarian was used earlier in a sense “scribe” (1660s).