application (n.) Look up application at Dictionary.com
early 15c., "the bringing of something to bear on something else," from Old French aplicacion (14c.), from Latin applicationem (nominative applicatio) "a joining to, an attaching oneself to; relation of a client to a patron," noun of action from past participle stem of applicare "attach to, join, connect," from ad "to" (see ad-) + plicare "to fold" (from PIE root *plek- "to plait").

Meaning "sincere hard effort" is from c. 1600. Meaning "a formal request to be hired for a job or paid position" is by 1851. Computer sense "program designed to carry out specific tasks or solve specific problems within a larger system" is a shortening of application program (1969).