... 律令制で「大戸・上戸・中戸・下戸」と呼ばれる四等戸の最下級である。
「戸」は課税の最小単位で、家族の人数や資産によって四等戸が決められていた。
婚礼時の酒の量が、上戸は八瓶、下戸は二瓶であったことから、酒が飲めない人を「下戸」と呼ぶようになり、酒をよく飲む人を「上戸」と呼ぶようになった。
日本のように貧富の差から飲酒量を喩えた言葉は中国にもあり、「大戸」や「小戸」と呼ばれている。

Among the types of families/houses (literally, 'doors') in the Ritsuryou system - namely the 'large house', 'upper house', 'middle house' and 'lower house' - this house ranked the lowest.

A 'house' ('ko') was the smallest taxational unit, and a 'house' would be decided according to the number of members in a particular family.

During weddings with alcohol, 'upper houses' would serve 8 bottles, and 'lower houses' would serve 2 bottles; and from this practice those who could not (afford to) drink alcohol came to be known as 'lower house', and those who could came to be known as 'upper house'.

In China, there are similar phrases to illustrate the stratification of wealth, i.e. 'large houses' and 'small houses'.