The rationale behind the Fn-Ctrl layout used on ThinkPads until very recently:

> The Fn key was originally placed by the ThinkPad designers in the lower left hand corner to make the key easier to locate when using the keystroke combinations. There was a rationale. This is especially handy for turning on the ThinkLight in the dark. Aim for the two extreme corners.

https://web.archive.org/web/20111115202457/http://www.lenovo...

IMO, putting Ctrl in the bottom left still isn't great for ergonomics: Ctrl should be where Caps Lock is, in line with the home row. This was the case on the original PC keyboard (IBM Model F) before it was moved to the bottom left in the Model M.

One of the only mass-produced keyboards that has Ctrl in this position today is the Apple Japanese keyboard: https://www.apple.com/shop/product/mxcl3j/a/magic-keyboard-u...