mid-12c., tresor, from Old French tresor "treasury, hoard, treasure" (11c., Modern French trésor), from Gallo-Roman *tresaurus, from Latin thesaurus "treasury, treasure" (source also of Spanish, Italian tesoro), from Greek thesauros "store, treasure, treasure house" (see thesaurus). In Middle English also thresur, etc.; modern spelling is from 16c. Replaced Old English goldhord. General sense of "anything valued" is recorded from c. 1200. Treasure hunt is first recorded 1913. For treasure trove, see trove.
late 14c., "to amass treasure; to store up for the future," also figurative, "regard as precious, retain carefully in the mind," from treasure (n.). Related: Treasured; treasuring.