There are some important K spelling patterns from Old English. At the beginning of words the letter K is silent before a letter N. However in Old English KN- at the front of a word was fully pronounced, and spelt CN-. The word knot came from the Old English cnotta. Other examples include: knife (cnif), knight (cniht) and knew (cneow). In Middle English the Norman French rulers of England changed the spelling from CN- to KN-. In Early Modern English it was reduced by lazy English speakers to an N sound. By 1750, silent K became the standard pronunciation after about a century of weakening.
Old English used a CC spelling at the end of many words which became a CK in Middle English. So words like sack come from the Old English word sacc. When does one use a C or a CK in Modern English spelling? There is no firm rule, however as a general guideline, the letter K replaced the letter C after a long vowel (peak, make), diphthong (hawk, book) or a consonant (risk, bank). After a short vowel, the Middle English -CK is used to represent the K-sound (back, lock, stack). Words of both Old French/Latin origin and Old English origin often got respelled to fit this pattern. However many words that used to be spelt with a -CK ending eventually were shortened to -C, examples include musick and publick. So the pattern exists, but not all words follow it.
The letter C usually makes a K-sound (instead of an S-sound) before A, O or U. At the beginning of words the letter K is silent before a letter N. At the end of words -CK is often used for the K sound. In the last article we covered when C makes a K or an S sound. (link.mingpao.com/69202.htm) In the next article, we will cover K sound spelling patterns that were brought to English by foreign words.