I discovered [Yublin](https://jonaquino.blogspot.com/2007/06/yublin-shorthand-for-speed-writing.html?m=1 https://jonaquino.blogspot.com/2007/06/yublin-shorthand

I discovered [Yublin](https://jonaquino.blogspot.com/2007/06/yublin-shorthand-for-speed-writing.html?m=1 https://jonaquino.blogspot.com/2007/06/yublin-shorthand-for-...) a while back which set out to do exactly this: create 1-3 letter shorthands for the 600 most common words in English. And sure enough, "the -> t" is at the top of the list.