We switched the letters
t and
f because
th is the most common pair of letters in the English language. (This is called a
digraph ). If you look at your keyboards, you'll see that right now, our keyboard is laid out as FGH. However, when we switch the spots of
t and h , t will be closer to h. We decided to leave a key between t and h for better accuracy on the mobile keyboard. We didn't want fingers jamming into each other.