Metal Monkey month
Historical term from the traditional calendar. Refers to a lunar month that contains a day of the Metal Monkey (庚申), which occurs roughly every other month. It was believed that colds were more frequent during such months.
See also: 庚申
In the old calendar, the Metal Monkey month was considered a month when one was prone to catch colds.
Compound of 庚申 (Metal Monkey, the 57th term of the sexagenary cycle) and 月 (month). The term originates from traditional East Asian calendrical beliefs associating certain days with health outcomes.