The word dram is a contracted form of the word drachma from Late Latin and Old French. In middle English the word was dragme. It was originally used to describe a minute quantity of something.
Druggists and apothecaries used the word dram as a unit of measurement meaning 1/8 of an ounce, or sixty grains.
The U.S customary system, which uses the Avoirdupois mass (weight) units, uses the dram (drachm) to mean 1/16 of an ounce, or 27.34 grains.
Notice that both the Apothecaries and the Avoirdupois systems use the grain as a basic unit of mass.
They both also have ounces, but as you can see, the relationship between grains and ounces is different in each.
In case you are wondering, the US Customary System and the British Imperial System are identical, except that they differ when it comes to units larger than a pound.
Similar to the British pound, when the value of coins was based on the actual amount of precious metal they contained, the word dram was sometimes used to describe a monetary unit, and still is today, in some countries, such as Armenia, where 100 Luma equals one Dram and there are dram coins valued from three up to 500 Dram.
In fact, dram as a way of describing money or treasure, is mentioned in the Bible in 1 Chronicles 29.7. There, the writer (which may have been Ezra), uses the word as a familiar way of describing an amount of treasure for “The service of the house of God” in the days of David:
And gave for the service of the house of God of gold five thousand talents and ten thousand drams, and of silver ten thousand talents, and of brass eighteen thousand talents, and one hundred thousand talents of iron. – (King James Version)
Later English Editions of the Bible sometimes replace the word dram with daric.
Later on in the bible, dram it is used to describe the Persian daric. The Hebrew words originally used were probably adarkon and darkemon and the Greek word for this was dareikos. This coin was currency among the Jews after their return from Babylon while under Persian domination. It was about 128 Troy grains (about 15 grams or 1/2 oz) and is one of the oldest, if not the oldest, coin mentioned in any written history.
For instance, in the book of Ezra 2.69:
They gave after their ability unto the treasure of the work three-score and one thousand drams of gold, and five thousand pieces of silver, and one hundred priests’ garments.
Dram is also mentioned in Ezra 8.27.
And also in Nehemiah 7.70-72:
And some of the chief of the fathers gave unto the work. The Tirshatha gave to the treasure a thousand drams of gold…
There are several more mentions through verse 72.
Although the word dram was originally used colloquially to mean a small quantity of anything, it eventually came to be used primarily to describe an amount of liquid of drink, specifically the amount of liquid drunk all at once. For instance, you might have heard, “I’m dying of thirst, can you give me a dram of water?”
At some point, during the 1800’s, dram came to refer only to spirits, rather than any drink and a dram was both the drink itself, such as whiskey, or the act of drinking it. So, to dram was to drink drams, usually referring to small drinks, such as taking a “dram of brandy.” A person who imbibed regularly was known as a dram-drinker.
Dram is often thought of as a Scottish word and is found in the name of the Scotch Whiskey liqueur, Drambuie and liqueurs were also called sweet drams.
The word was also used to name a Jamaican allspice flavored rum liqueur, called Allspice dram, Jamaican dram, or Pimento dram.