Probably typing on a non english keyboard. When I learned C a long time ago, I read somewhere 'isnt it nice that one doesnt need a lot of keystrokes like for begin and end', and I thought pls give me begin and end instead of this unpleasent slow hand movement.
Spot on. It's the reason many non-native speaker developers I know nevertheless use an English keyboard layout. I personally made my own hybrid layout that is basically an English US layout with the letters rearranged according to my native layout.
The author was born and raised in Brooklyn and went to Cornell, if I remember correctly. As far as I know, English was his only language, and he was almost certainly using either US QWERTY or Dvorak keyboard layout.