Complex sentence: "Billig" was only the commercial name of one of the first and best-selling crepe griddles ever made, but soon turned to a common name and is now even found in Breton and French dictionnaries as a synonymous for "crepe maker".
Split into simpler sentences: Billig was only the commercial name a crepe griddles model, which due to high popularity turned to a common name. It is now found in Breton and French dictionnaries as a synonymous for "crepe maker".