It's so weird. It looks like it should be pronounced (ga-no-mm), but it's pronounced (no-mm). See also #why.
A stubborn person who insists on making an error in spite of being shown that it is wrong.
Supposedly, this insult originated with an illiterate priest who said mumpsimus rather than sumpsimus ("we have taken" in Latin) during mass. When he was corrected, the priest replied that he would not change his old mumpsimus for his critic's new sumpsimus. See also Error, Stubborn.
i found this funny because some people are so old in jokes so yh that's to them people *yolo See also Dry People.