Emily Udell, one of the reporters at my paper, pointed out something interesting to me last week:
I am working up a blog entry about a new Pew study on how much money states spend on incarceration versus programs for people on parole or probation. I knew the word for a person on parole was a parolee, but probationee didn't sound quite right. I discovered that the proper word is probationer, which sounds like it means a person who grants probation to another. I thought that was kind of interesting -- parolees and probationer.
This is interesting. I guess it's kind of like the British word for retiree, which is pensioner. I looked probationer up in four dictionaries and three usage guides, but none explained why -er is the proper suffix here. Probably just one of those things in English that just is.
You can read the blog here. It's the March 3 entry.