Meaning

noun a unit of apothecary weight equal to an eighth of an ounce or to 60 grains

noun a British imperial capacity measure (liquid or dry) equal to 60 minims or 3.5516 cubic centimeters

noun a unit of capacity or volume in the apothecary system equal to one eighth of a fluid ounce

originBorrowed into late Middle English from Old French dragme (modern French drachme), from Late Latin dragma. Doublet of dirham.

Etymology from Wiktionary, CC BY-SA 3.0