Why was "tantrum" trending last week?
"put to practical use," (as opposed to abstract or theoretical), 1650s, from past participle of apply. Earlier it was used in a sense of "folded" (c.1500).
late 14c., "to put (one's faculties, etc.) to some task or career," late 14c., from Old French aploiier "apply, use, attach" (12c., Modern French appliquer), from Latin applicare "attach to, join, connect;" figuratively, "devote (oneself) to, give attention," from ad- "to" (see ad-) + plicare "fold" (see ply (v.1)). The etymological sense is "bring things in contact with one another." Of lotions, from early 15c. Meaning "seek a job by submitting an application for one" is from 1851. A by-form applicate is recorded from 1530s. Related: Applied; applying.