assay (n.) Look up assay at Dictionary.com
mid-14c., "trial, test of quality, test of character," from Anglo-French assai, ultimately from Late Latin exagium "a weighing" (see essay (n.)). Meaning "trial of purity of a metal" is from late 14c.
assay (v.) Look up assay at Dictionary.com
c. 1300, "to try, endeavor, strive; test the quality of," from Anglo-French assaier, from assai (n.), from Old French assai, variant of essai "trial" (see essay (n.)). Related: Assayed; assaying.