I knew there were more 2-letter words than most folks think of, but I didn't know there are 101. According to Stephin Merritt's introduction to 101 Two-Letter Words, the official list of "acceptable" words you can use playing Scrabble® is 101.
Anyway, Merritt is a songwriter, and a fast hand with a rhyme, so when he found himself writing cute quatrains for various 2-letter words, he decided to do them all. With the help of Roz Chast, whose cartoons you might have seen in New Yorker and elsewhere, 202 pages were occupied with the rhymes such as this one for HO:
"Ho, ho, ho," says old Saint Nick,
But saint for what, exactly?
Mayhap for hopping round the world
and getting back intactly.
And here is Santa upon his return. I reckon you can see why I call the work of Ms Chast "charmingly ugly".
And I applaud them both for picking this meaning for HO in preference for another of more recent vintage.
It is interesting, of 676 possible 2-letter combinations, nearly 15% are considered words. I reckon that is the highest percentage going. But even a lower percentage for 3-letter words would still pile up to a lot, as there are 17,576 to start with, and nearly 1,300 (7.4%) that the Scrabble® folks count. That would make for a much bigger book.