In fire protection engineering, a Siamese connection is a pipe fitting that allows two fire hoses to be connected to a single standpipe riser at the same general location. It is so-called due to the visual allegory to Siamese twins.
Ramsey, Charles; Hoke, John Ray, Jr. (ed) (2000). Architectural Graphics Standards (10th Edition). John Wiley & Sons, Inc.. ISBN 0-471-34816-3.