from The Century Dictionary and Cyclopedia
- n. A valve in which the ports of entrance to the two ends of the cylinder are near the heads of the latter, and the valve itself is of two pieces in effect joined together by the hollow tube which is called the trunk. The modern form of this valve is the hollow piston valve, in which the two pistons forming the valve proper are connected by a hollow rod. Also called Murdock's slide-valve.
Sorry, no etymologies found.