Old English/Language Change

In many cases, it is possible to guess the Modern English form of a word—and thereby perhaps a hint as to its meaning—by applying regular sound and spelling changes. Sometimes this process can be done in reverse to guess the Old English form of a Modern English word, though this is by no means reliable, especially since it's not always obvious whether a Modern English word came from Old English in the first place. ā → oa or long o: rād → road; bāt → boat; stān → stone; bān → bone ē → ee: fēt → feet ō → oo: fōt → foot; bōc → book; gōs → goose ū → ow/ou: cū → cow; hū → how; dūne → down; þū → thou; mūs → mouse h → gh: cniht → knight; rūh → rough; tōh → tough; þurh → through (this one exhibits metathesis of the r)