noun
unofficial era name; private era name
Historical term for era names created and used by commoners or local regions, not by the imperial court. Often contrasted with official era names (元号).
江戸時代には、朝廷が定めた元号とは別に、民間で私年号が使われることがあった。
In the Edo period, private era names were sometimes used among commoners separately from the official era names set by the imperial court.
This old document records an unfamiliar unofficial era name.