mid-15c., "small weight of apothecary's measure," a phonetic spelling, from Anglo-Latin dragma, Old French drame, from Late Latin dragma, from Latin drachma "drachma," from Greek drakhma "measure of weight," also, "silver coin," literally "handful" (of six obols, the least valuable coins in ancient Athens), akin to drassesthai "to grasp." The fluid dram is one-eighth of a fluid ounce, hence "a small drink of liquor" (1713); Hence dram shop (1725), where liquor was sold by the shot.
dram (drām)
n.
Abbr. dr
A unit of weight in the U.S. Customary System equal to 1/16 of an ounce or 27.34 grains (1.77 grams). Also called drachm.
A unit of apothecary weight equal to 1/8 of an ounce or 60 grains (3.89 grams).
The Authorized Version understood the word 'adarkonim (1 Chr. 29:7; Ezra 8:27), and the similar word darkomnim (Ezra 2:69; Neh. 7:70), as equivalent to the Greek silver coin the drachma. But the Revised Version rightly regards it as the Greek dareikos, a Persian gold coin (the daric) of the value of about 1 pound, 2s., which was first struck by Darius, the son of Hystaspes, and was current in Western Asia long after the fall of the Persian empire. (See DARIC.)
unit of weight in the apothecaries' and avoirdupois systems. An apothecaries' dram contains 3 scruples (3.888 grams) of 20 grains each and is equal to one-eighth apothecaries' ounce of 480 grains. The avoirdupois dram contains 27.344 grains (1.772 grams) and is equal to one-sixteenth avoirdupois ounce of 437 12 grains. The term also refers to the fluid dram, a measure of capacity equal to one-eighth fluid ounce.