Also, all these usages of "ough" come from the Anglo-Saxon letter "yogh" (originating, I think, as a rune, and written rather like the number 3.) It was adopted by early English scribes as a phoneme for a glottal fricative that did not exist in Latin, and therefore had no equivalent in the Latin alphabet. But later, with the invention of printing and the increasing latinization of written English, these borrowed runes were replaced with rough transliterations (like "rough") of the letter "yogh" into Latin letters. So for example, "fo3t: became "fought" (etc.)

Another example of this is the Thorn, which was written as a "p" with a handle to the north (like a "b") as well as to the south. This, of course, was later transliterated into the Latin alphabet as "TH"

This was similar to what Latin authors did when they translated Greek words that begin, say, with Phi, into PH to capture the vaguely plosive "p" sound that had no equivalent in Latin, and was later normalized to a labial fricative (F).