Carolingian G

The other form scholars and writers familiar with Celtic Britain generally knew and could use, and in the furthest places in Britain away from England exclusively used domestically, was the insular (or Irish) G, which could bear a well-understood extra phonetic sense, when writing of the local people, places and language.

Unlike the vowel u and consonants which could appear ambiguous such as s, it had no special rules as to choice of letter in Middle English orthography.

[1] Its forms, varying little, are the basis of and frequently match the modern letter G. Insular G evolved very largely into digraphs gh, ch, but in its early days some writers used it for yogh.

By the 18th century, the script had 26 base characters for letters (with upper case counterparts) promulgated by most major printing presses and taught in alphabet nursery rhymes.

Despite this widening across most, then almost all, formal teaching in Europe, g has a quite diverse phonetic value across languages following its development from c, which shares this trait.