Interesting. I was always curious about the writing near the doors on buses that said ワンマン ("one man"). It seemed an unusual thing to announce on the outside of the bus. Were there even such things as "two man" buses? Does it harken back to a time, decades ago, when there was one person on the bus who drove the bus, and another who collected the fare? And if so, was it really necessary to announce on all buses in this day and age that the current bus configuration was a "one man" bus? Who could that sign possibly be helping? Without that sign, what sort of confusion was the bus company anticipating? And yet there it was, on all the buses. ワンマン. I don't know if its still put on the outside of buses, but old habits die hard, and I suspect it still lurks on many, if not most buses.
As an occasional critic of over-katakanization of Japan, this in particular stood out as an example of unnecessary use of katakana English that was kept alive by momentum rather than a rational business need.
ワンオペ must be the descendent of ワンマン, but for some reason ワンオペ doesn't grate on me as much as ワンマン. In fact, I like how its been coopted to become a euphemism for single-parent. It somehow takes that rather dry description and adds the element of having to manage a large burden of work by oneself. I'd never heard it until today.