The word "carbonian" does not exist in the English language, therefore, there are no synonyms to it. One possible explanation for its non-existence could be an error in spelling or usage. However, there are synonyms for the word "carbon" which is derived from the Latin term "carbo" meaning coal. These synonyms include charcoal, soot, coal, and graphite. Carbon is an essential element in nature that plays a significant role in various industries, including construction, energy, and manufacturing. It is a versatile material that can be found in various forms, from diamonds to pencils.