Why do we spell it "knight"?

The word "knight" gets its strange spelling, like many present-day English words, from sound shifts throughout history.

A long time ago, in the Old-English era, it was spelled "cniht", and pronounced exactly as it was spelled. The "h" made a rhaspy sound, which subsequently became represented in English as the "gh". The "c" also becamea a "k", just by chance. When spelling became fixed in the English language (a process that began, perhaps, when the printing press arrived in England in the 1400s), people still pronounced "knight" this way, although the sound of the "i" was changing from the sound in "hit" to the sound in "height". Over the centuries, many words in English lost sounds, including "knight", for a variety of reasons. As spelling had been more or less fixed, these changes were not reflected in the spelling. Doubtless, people tried to halt this sound change, parents reprimanding their children for not pronouncing the "k" at the start. In the end, they did not succeed, and "knight" became one of many English words famous for their unconventional spelling.