Giuseppe Peano was, in his time, a towering mathematical genius. He was also a man who did a number of very unusual things - like making up a language, and insisting on lecturing his college students in it.
Giuseppe Peano's life spanned the last part of the 19th century and the first part of the 20th century. He did not take a lot of time off, in either century. Peano was the author of over 200 works, most of them done while he was teaching at the University of Turin. He didn't do mediocre work at either job. Bertrand Russell, also no slouch when it came to producing impressive work, credited Peano's lectures with changing his life.
Russell may not have felt the same if he went to Peano's later lectures. It's not that Peano didn't keep working. It's just that his work took a new direction. Peano wanted to build a universal language, a goal shared by many people, before and since. Latin was the accepted academic language, and the influence on a number of languages around Europe, so Peano decided to use it as a base. What he came up with was Latino Sine Flexione. That is "Latin without flexions."
Flexions are the fiddling bits of the language. They are what make you say "cars" instead of "car," when you are dealing with more than one car. Peano thought that if you specified that there were three cars, everyone already knew you meant a plurality of cars, so you shouldn't have to modify the noun. You should be able to say "three car." He also simplified verbs, to get away from the misery of when one form, or tense, of the verb is nothing like another. (For example, in English, the word "to be" is nothing like "I am," which is nothing like, "I was," and is nothing like, "they are." Peano's language tried to simplify verbs so, if you knew the infinitive of the verb, you knew how to conjugate it.)
This was all well and good. The idea of making a universal language was popular around the turn of the century. Peano's language was criticized by some, modified by others. Peano liked it just as it was, and did his best to popularize it. His best involved insisting on giving all his lectures in it. He would get a class in, and then lecture them, at length, in his own version of modified Latin, which they had not studied. Students weren't wild to attend the class of a lecturer who tried to guide them through a complicated subject in a language they could not understand. Peano became increasingly isolated towards the end of his life, but perhaps he preferred it that way.