Why do English German and some Scandinavian languages use two letters ck to point the sound k in cases?

The use of "ck" for the "k" sound in these languages is a historical spelling convention that evolved over time. In Old English and Old High German, the combination "ck" was used to represent the "k" sound, and this convention continued in modern English, German, and some Scandinavian languages. It is a way to differentiate the "k" sound from the "c" sound when followed by certain vowels.