An Etymological Dictionary of Astronomy and Astrophysics

To make use of; to put to use especially for some practical purpose.

To put into operation or effect.

To lay or spread on; to be placed or remain on.

To make a request especially in the form of a written → application.

Etymology (EN): From M.E. ap(p)lien, from O.Fr. aploiier “apply, use, attach,” from L. applicare “to attach to, connect;” figuratively, “devote (oneself) to, give attention,” from → ad- “to” + plicare “to fold,” → explain.

Etymology (PE): Âtâhidan, from â- intensive/nuance prefix, + tâh “fold, plait, ply” (on the model of L., as above, → explain);
Mid.Pers. tâg “piece, part” + -idan infinitive suffix.
Bé kâr bordan, from bé “to; for; in; on; with; by; according to,” → ad hoc; kâr, → work, bordan “to carry, bear, conduct, take,” → range.