Accessioning

the act of coming into the possession of a right, title, office, etc.:
accession to the throne.
an increase by something added:
an accession of territory.
something added:
a list of accessions to the college library.
Law. addition to property by growth or improvement.
consent; agreement; approval:
accession to a demand.
International Law. formal acceptance of a treaty, international convention, or other agreement between states.
the act of coming near; approach.
an attack or onset, as of a disease.
to make a record of (a book, painting, etc.) in the order of acquisition.
to acquire (a book, painting, etc.), especially for a permanent collection.
Historical Examples

A description of the operation of accessioning in the New York public library (Reference department) is enclosed as a sample.
Papers and Proceedings of the Thirty-fourth Annual Meeting of the American Library Association Held at Ottawa, Canada June 26-July 2, 1912 Various

He also began the accessioning and shelf marking of the books.
Report of the Chief Librarian J. O. Wilson and General Assembly Library (New Zealand)

Note—In the decision to replace, the labor of accessioning and withdrawal must always be taken into account.
Mending and Repair of Books

Margaret Wright Brown

Its system of accessioning will be abandoned as soon as possible.
Papers and Proceedings of the Thirty-fourth Annual Meeting of the American Library Association Held at Ottawa, Canada June 26-July 2, 1912 Various

noun
the act of entering upon or attaining to an office, right, condition, etc
an increase due to an addition
an addition, as to a collection
(property law)

an addition to land or property by natural increase or improvement
the owner’s right to the increased value of such land

(international law) the formal acceptance of a convention or treaty
agreement; consent
a less common word for access (sense 2)
verb
(transitive) to make a record of (additions to a collection)
n.

“act of coming to a position,” especially of a throne, 1640s, from Latin accessionem (nominative accessio) “a going to, joining, increase,” noun of action from past participle stem of accedere (see accede).