The Evolution of English Spelling

Before spelling became completely standardized, it was common to find lots of words in English where g-h was replaced with an F. For example, the word daughter is sometimes found with an F in the middle, suggesting that some people pronounced it as dofter. The word dough can also be found with anF pronounced as duff; that pronunciation still survives in the name of a traditional English dessert called plum duff. Those various pronunciations were sorted out over time with some words like laugh, cough, tough retaining that F sound. But in most cases, the sound was lost altogether.