"Duo-denary" is an uncommon word that refers to a group of twelve. However, there are several synonyms for this word that are more commonly used. One such synonym is "duodecimal," which is derived from the Latin word "duodecimus," meaning "twelfth." Another synonym is "dodecad," which is derived from the Greek word "dodekados," also meaning "twelve." Additionally, the word "dozen" can also be used to refer to a group of twelve. While "duo-denary" may be a more obscure term, these synonyms provide more accessible and widely-used options to describe a group of twelve.