Doughty is a persevering English word. In Old English, it shows up as dohtig, which was probably an alteration of dyhtig that resulted from the influence of the Old English dohte, meaning "had worth." By the 13th century, the spelling doughty had begun to appear. The expected pronunciation would be \DAW-tee\, paralleling other similarly spelled old words like bought and sought. But over the centuries, the spelling was sometimes confused with that of the now-obsolete word doubty, meaning "full of doubt," and thus, so it is conjectured, we have the pronunciation we use today.