ETYMOLOGY OF THE TERM "DEMIJOHN"
The origins of the terms "demijohn" and "carboy" are interesting as they shed light on the historical details of their manufacture and use.
McKearin and Wilson, in their book AMERICAN BOTTLES & FLASKS AND THEIR ANCESTRY, provide this account:
Sometime about the middle of the 18th century, two new names entered the language to designate large glass bottles, usually wickered and used for transport of liquids. They were "demijohn" and "carboy," which were used sporadically by merchants and bottle manufacturers before the 19th century. "Carboy" was used far less often than "demijohn," at least in advertisements. Also, it would seem, neither was admitted to a dictionary until well into the 19th century.
According to accepted derivation, "carboy" was a corruption of the Persian "garabah"; "demijohn" of the old French "dame jeanne," as large bottles were called. Though the spelling of "carboy" apparently was consistent, that of "demijohn," perhaps because it was spelled mainly from its sound when spoken, was most unsettled before 1815; "demi-john," "demi jeanne," "Dame John," "dime-john," "Demie-John," "Demi John," "Demy John," "dimijohn," and "demijohn." "Demijohn," which became official, occurred most frequently.
In the newspaper advertisements covered, the name was not found until 1762, but in 1753 "wickered bottles wthat will hold 5 gallon" were advertised -- demijohns, of course -- which suggests that "demijohn," however spelled, was unfamiliar before the 1760s. In fact, THE OXFORD ENGLISH DICTIONARY (1933) gives 1769 as the date of its first appearance in print, and for "carboy," 1753, fourteen years before it was found in the advertisements.
In 1767, carboys ranging from a quart to seven gallons in size were offered to the public, and in 1792 demijohns of eight and nine gallons containing spirits of turpentine. The two names, it would seem, were used interchangeably in the eighteenth century, and for the same sizes of bottle. Afterward, the majority of demijohns were bottles from a quart to five gallons in capacity, a few up to ten gallons; carboys were principally a gallon to twenty gallons, with sizes from six gallons predominating.
And demijohns, wickered, were destined to contain non-corrosive and bland liquids, whereas carboys, set in very heavy wicker "tubs," were for acids and chemicals.