The term Siamese Twin is derived from the famous Chang and Eng Bunker, who were joined at the chest. They were born in Siam in the early 19th century, and the term "Siamese" was used to describe anything that was unusual. Nowadays, the term is considered offensive, and people prefer to use different words. One of the most commonly used synonyms is "conjoined twin," which is a medical term and more precise. Other synonyms include "twin sharing a body," "twin parasite," and "fused twin." It's essential to use appropriate words while addressing people with conjoined twins, as language plays a vital role in respectful communication.