"toaster" is pretty common argot for "low-power computer"

After the Power Mac g4 cube came out, that form factor became a trend for a little while.

https://i1.wp.com/www.mac-ave.com/wp-content/uploads/2016/11...

I immediately thought of this: https://www.embeddedarm.com/blog/netbsd-toaster-powered-by-t...

It's an actual toaster running NetBSD.

that seems kind of oxy-moronic? aren't toasters horribly energy hungry?

The comparison is in the computing power needed to control a toaster, not to toast the toast.

I would have defined toaster as "slow, horribly outdated computer". That also fits your toaster comparison since old computers are very energy hungry compared to similarly speced modern computers.

I have a white EeePC 901. While I was still using it as my carry-around laptop, it was called "Toastie", because it looked kind of like a sandwich toaster.