What do you mean by "mother also"?

It is best understood from the context.

His mother should mean, his mother

There is a saying that it is a great achievement for a scholar to teach intellectuals. Because of the good handwriting, there is an endless stream of people asking for words. He said he couldn't finish it at home every day, and he couldn't finish it elsewhere. Often when you are anxious and helpless, there will be a classical Chinese national curse-"It's also a mother!" That is, the vernacular "damn it", see Jiang's "Questions and Answers to the National Scold".

The legend about Qigong's "mother also" goes like this:

One day, some graduates went to Mr. Qi Gong's house and asked him to write an inscription on the paper. At this time, a governor came to visit with his secretary and put on airs with the students, saying that he loved calligraphy. He especially learned from Mr. Qi Gong, asked for a word, not too big, six feet was enough, and opened a word he had written for everyone to appreciate. Mr. Qi Gong doesn't think so. He asked others, what are the good words for writing for a leading official? Someone whispered, "So is mother!" Qi Gong smiled and said, "Good" the secretary brought by the governor is quite cultured. When he heard something bad, he agreed to let the governor go. Tell me, in fact, some cultures are unnecessary, and secretaries are still very sensitive to the atmosphere, hehe.

"Mother is also!" Translated into vernacular, it means "Shit!" I think this student is also an advocate of practical jokes, which coincides with the childlike innocence of Qigong, so he made a joke and really let Qigong be written on paper. It is estimated that it can be enforced by tying hands in the way of the Cultural Revolution.