Here's a fun typography fact for you: Old English and Middle English had a single character for the "th" sound, called thorn. It looked like Þ in the capital; the lowercase is þ.

(If you crossed the upper bar, like so: Ꝥ ꝥ , it was shorthand for "that". "I like ꝥ kitten.")

Thorn largely died out when printing presses were imported to England. Because the typefaces were from Germany or Italy, they didn't have thorn. So they replaced it with a letter ꝥ rarely occurred in the same place þ did: Y.