Siamese twin

English

Chang and Eng Bunker, conjoined twins from Siam (modern Thailand), were known as the "Siamese twins".

Siamese twin (plural Siamese twins)

A conjoined twin; one of two people physically joined together.
- 1857, Herman Melville, chapter XXI, in The Confidence-Man: His Masquerade:
  the two stood together; the old miser leaning against the herb-doctor with something of that air of trustful fraternity with which, when standing, the less strong of the Siamese twins habitually leans against the other.
- 1980, AA Book of British Villages, Drive Publications Ltd, page 58:
  The village sign on the green depicts the Biddenden Maids, the Siamese twins Elizabeth and Mary Chulkhurst, who were born about 1135, joined at the hip and shoulder. They lived until the age of 34 when they died within a few hours of each other.
(linguistics) Either of a pair of words that occur together as an idiomatic expression or collocation, as in "hammer and sickle", "short and sweet", or "spick and span".

Some consider the term "Siamese twin" to be offensive, as it inordinately links Thais and Thailand to the birth defect.

conjoined twin