keyboard short cut 'E' and 'O' of terminal emulator 'terminator'

Question

I'm not sure this kind of question is acceptable here.
I'm thinking of trying terminator.(https://www.tecmint.com/terminator-a-linux-terminal-emulator-to-manage-multiple-terminal-windows/)
The hot key to split the window horizontally is ctrl+shift+O and vertically is ctrl+shift+E. Where do the key E and O come from? Is it from German eben and oben? (I've learned some German and in German eben sounds like "to the side" and oben sounds like "above".) Having said that, I think I can remember the key now. :)

Answer 1

The manpage uses bold formatting to show why:

Ctrl+Shift+O
      Split terminals Horizontally.
Ctrl+Shift+E
      Split terminals Vertically.

The second letters in "horizontally" and "vertically" are o and e respectively. Since this is how it was since the keyboard shortcuts were first added to the manpage in 2008 (before the 0.10 release), I think that's pretty much it.