function (n.) Look up function at Dictionary.com
1530s, "one's proper work or purpose; power of acting in a specific proper way," from Middle French fonction (16c.) and directly from Latin functionem (nominative functio) "a performance, an execution," noun of action from funct-, past participle stem of fungi "perform, execute, discharge," from PIE root *bheug- (2) "to use, enjoy" (see brook (v.)). Meaning "official ceremony" is from 1630s, originally in church use. Use in mathematics probably was begun by Leibnitz (1692). In reference to computer operations, 1947.
function (v.) Look up function at Dictionary.com
1856, "perform a function" (intransitive), from function (n.). Related: Functioned; functioning.