Who wrote Alma mater?

There isn't a single author of the phrase "Alma Mater". It's a Latin phrase that means "nourishing mother" and has been used to refer to one's university or school for centuries.

The phrase likely originated in ancient Rome, where it was used to refer to a goddess who was considered the protector of a city. Over time, it was adopted by universities to symbolize the nurturing and educational role they played in the lives of their students.

While no one person can be credited with "writing" the phrase, it was popularized in the 19th century by universities who adopted it as their official motto or part of their school song.

So, while there's no single author, the phrase "Alma Mater" has been used for centuries and has become a universal symbol of a university's role in its students' lives.