Although griffonage is unrelated to the mythical beast, why do we associate birds with poor handwriting, e.g., the part-bird griffon and chicken scratch? We use bird plumes to write, but we associate bird feet with scratchy, illegible writing.
To someone coming unawares upon this word, it might seem to have a connection to that fabulous beast called the griffin or gryphon, the one with the head and wings of an eagle and the body of a lion. Or might it perhaps refer to the vulture with that cognomen or breeds of dog similarly named, both of which derive from an older English spelling of griffin? Alas, no. It’s more prosaic than that.
Readers with knowledge of French will be at an advantage, since the word appears in that language, as griffonnage, a noun that is formed from the verb griffonner, to scribble or scrawl. A griffonage is therefore an illegible scrawl.