mid-14c., "authority entrusted to someone, delegated authority or power," from Old French commission and directly from Latin commissionem (nominative commissio) "act of committing," in Medieval Latin "delegation of business," noun of action from past participle stem of committere "to unite, connect, combine; to bring together," from com "with, together" (see com-) + mittere "to release, let go; send, throw" (see mission).
Meaning "document delegating authority" is from early 15c.; meaning "body of persons charged with authority for the performance of certain special duties" is from late 15c. Sense of "anything entrusted to anyone to perform" is from 1560s; sense of "act of committing or doing" is from 1590s.
Naval sense "period of active service of a warship" is by 1882 (in commission "under the command of an officer" is from 1733). Hence out of commission "laid up in a navy yard or in reserve" (1878), subsequently extended to other machinery, and, figuratively, to persons or human qualities by 1917.
In commercial use, "authority delegated by another for the purchase and sale of goods," 1620s. Meaning "allowance made or percentage given to an agent for transacting business" is from 1725.
1660s, "empower or authorize by commission," from commission (n.). In the naval sense, of persons, "be given the rank of an officer (by commission from authority)," from 1793; of a ship, "to be transferred from the naval yard and placed in the command of the officer put in charge of it," 1796. Related: Commissioned; commissioning.
early 15c., "one appointed to perform some business by a commission from a proper authority," from Anglo-French commissionaire, from or on the model of Medieval Latin commissionarius "one entrusted with a commission," from commissionem "act of committing," in Medieval Latin "delegation of business" (see commission (n.)).
Meaning "member of a commission" is from 1530s, especially "person elected to manage the affairs of a municipality." Short form commish is attested by 1910 (earlier it was short for commission).