noun
one hour (archaic time unit)
Archaic term for a unit of time equal to one modern hour. Used in historical contexts, especially in reference to the traditional Japanese temporal system where a day was divided into 12 'hours' of varying length. Not used in contemporary Japanese; the modern word for 'one hour' is 一時間 (いちじかん).
江戸時代には、一刻が約二時間で、時中はその半分にあたる。
In the Edo period, one 'koku' was about two hours, and 'tokinaka' was half of that.
Compound of 時 (とき, 'time') and 中 (なか, 'middle' or 'half'), literally 'half of a time period'. The exact historical derivation is uncertain, but it likely referred to half of a traditional temporal unit (一刻).