To me, "on the bare" has a ritualistic flavor. It's not all that rare for ritualistic phrases or cliches to be shortened in ways that don't make sense on their own merit. The worst example I can think of offhand is shortening, "I couldn't care less," to, "I could care less," which is nonsensical unless maybe it would be spoken in an ironic tone. In a ritualistic setting, it's not difficult to imagine the phrase, "on the bare bottom," being used often enough for a long enough period of time that somewhere along the line, people got into the habit of shortening it. That's how I interpret the phrase when I encounter it.
If I would get picky, I would say using "on the bare" doesn't ring true in most family settings or in institutional settings where there isn't any particular traditional ritual regarding how spankings are administered. But it feels like a good fit to me in a school with a longstanding tradition of carrying out corporal punishment in a ritualistic way. |