K, (kā), the eleventh letter of the English alphabet, is nonvocal consonant. The form and sound of the letter K are from the Latin, which used the letter but little except in the early period of the language. It came into the Latin from the Greek, which received it from a Phœnician source, the ultimate origin probably being Egyptian. Etymologically K is most nearly related to c, g, h (which see).
In many words of one syllable k is used after c, as in crack, check, deck, being necessary to exhibit a correct pronunciation in the derivatives, cracked, checked, decked, cracking; since without it, c, before the vowels e and i, would be sounded like s. Formerly, k was added to c in certain words of Latin origin, as in musick, publick, republick; but now it is omitted.[1913 Webster]
See Guide to Pronunciation , §§ 240, 178, 179, 185.[1913 Webster]