noun
previous ruler; previous lord; late lord
Historical term for a former ruler or lord, often used in feudal contexts. Not used in modern everyday speech.
先公の時代には、この地は栄えていた。
In the time of the previous lord, this land prospered.
Colloquial and derogatory term for a teacher, used mainly by students in a mocking or disrespectful way. Often written in kana.
あの先公、宿題出しすぎだよ。
That teacher gives way too much homework.
せんこうに怒られた。
I got yelled at by the teacher.
Katakana variant, mainly for search coverage.
The kanji 先 (previous) and 公 (lord, prince) combine to mean 'previous lord'. The derogatory teacher sense likely developed as slang among students, using the same kanji with a mocking tone.