I was listening to NPR today and Mara Liasson said that the Trump administration was "pushing the edge of the envelope." I was struck by this as I hadn't heard this particular mash up prior. This reminded me of two other examples of idioms that have expanded and I merely wanted to muse for a moment on the idea.
To be clear, the idiom in question is "pushing the envelope" and somehow "the edge" got added (pushing one over the edge? approaching the edge? razor's edge? cutting edge? leading edge?). Again, I'd never heard this particular mash up before, but it makes enough sense how it came about. I'm a little sensitive to idiomatic expansion because in high school I was called out for saying "on top of the ball" instead of "on the ball" or "on top of things." I don't know why I mashed it up, but I did, and now I think about it more than I should. So, yes, "pushing the edge of the envelope" set me on edge, if you will.
Sometime between these two events (high school and literally today) I came across David Mitchell's rant on "holding down the fort" which is the expanded idiom I hear the most. To summarize his piece - one should "hold things down" or "hold the fort", but to "hold down the fort" makes it sound like the fort is going to float away should you fail in your duty. It's stuck with me and I try to avoid the mash up, though I've heard someone else say it as recently as Saturday (I was left alone on a shift and asked to "hold down the fort").
Where am I going with this? Nowhere. I was thinking about it and wanted to type a few words in a row to get the thought out of my head. Hopefully I haven't got this idée fixe stuck in your head.
(I think that fails as an expanded idiom, but whatever.)