Sometime around the fifth century AD, changes occurred in the runes in Frisia (the area around the northern Netherlands and north-western Germany). This period coincided with the Anglo-Saxon invasions from this area and the appearance of similar runes in the British Isles. The forms of several of the runes changed, notably the runes for A/O, C/K, H, J, S, and Ng. Also, changes in the language led to between five and nine runes being added to the alphabet to compensate for the extra sounds, and several runes were given different corresponding letters. This alphabet has become known as the Anglo-Saxon Futhorc. (tara hill)