Sylabulus is a recurring character and term in early Hamumu titles; originally starting as a mishearing of syllabus. He is portrayed as an evil wizard and made his debut in the unreleased Mucho Kombat and later Boboli. The model used for Sylabulus was later repurposed for Mr. Wilkins. While Kid Mystic was in development, the 'Sylabulus' name would also be used for Kid Mystic's sprite, although Kid Mystic himself had no linkages with Sylabulus the evil wizard, other than the fact they're both wizards.
The 'Sylabulus' bot as featured in LoonyChat
The term still continues to be used by fans, such as in the LoonyChat discord for one of the reference bots.