on purpose, by design; intentionally: How could you do such a thing on purpose?
11.
to the purpose, relevant; to the point: Her objections were not to the purpose.
Origin: 1250–1300; (noun) Middle English purpos < Old French, derivative of purposer, variant of proposer to propose; (v.) Middle English purposen < Anglo-French, Old French purposer
Related forms
pre·pur·pose, verb (used with object), -posed, -pos·ing.
re·pur·pose, verb (used with object), -posed, -pos·ing.
un·pur·posed, adjective
un·pur·pos·ing, adjective
Synonyms 1. object, point, rationale. See intention.7. mean, contemplate, plan.
late 13c., from O.Fr. porpos "aim, intention" (12c.), from porposer "to put forth," from por- "forth" (from L. pro- "forth") + O.Fr. poser "to put, place" (see pose). On purpose "by design" is attested from 1580s; earlier of purpose (early 15c.).