G, as you know, is the 7th letter in the English alphabet. It is one of the youngest letters out of our 26 letter alphabet. It didn't become a separate letter until the time of the Romans. Before the Romans it was the same as the letter C.
The ancient Greek called their C gamma, and pronounced it like a G. The Etruscans gave their C the k sound, as in cat.
When the Romans adopted the Greek alphabet, they were very much influenced by the Etruscans; so they gave their C both the Greek G sound and the Etruscan's K sound. It proved to be very confusing, so they later introduced a new letter, G, to cover the words with the G sound, and kept the old letter C to the sound of K.
In some words, the "gn" is pronounced "n", as in gnat. It can also be pronounced "zh", as in some French origin words like beige or rouge.
A Few Meanings for G
*In architecture, seen in a lot of elevators, G stands for the "Ground Floor" or "General Floor", in other wordsthe main entrance floor.
*G stands for the color green in the RGB color model.
* G is a rating from Motion Picture Association of America, meaning the movie is appropriate for everyone to see.
*G is a note in music.
*In TV, G is a rating meaning it's appropriate for everyone.