My wife and I were talking about regional dialect, discussing such localized terms as "bubbler" or "the devil's beating his wife." Eventually, the conversation led to her use of new words with her students, but I was taken aback by the word she used. She said that she often tells her students that they are all going for their constitutional, and they always look at her like she's kind of nuts. At which point I kind of looked at her like she was nuts. She said that it meant to go for a short walk. She has to take students to other classes, recess, and lunch. 

My own definition, and I started to question my own memory now, was that a constitutional, or morning constitional, is using the bathroom. It's normally described as a bowel movement, but the link seems to be when you'd take that short walk to the outhouse in order to take care of business (which, of course, also does not mean what it claims.) When I thought about it, I could not identify wherther I'd heard of this usage from family, friends, movies, or what. Maybe it was a Hollywood Western. 

When I read about the use of a constitutional in online forums, it was clear that there were people (like my wife) who'd only heard of the term as a short walk. She'd read it in older novels from England. One forum response inferred it was British English versus American English, and many people made the outhouse reference. But none of the answers I found really explained the transition from a pleasant, short walk into a euphemism for sitting down at the office. I can't tell whether the first to change the meaning were English or American, and I also can't tell when that was, or if it ever happened, as in, what if a colorful writer wrote it into a modern American film about a past time? Interesting to consider.