LAYSHAFT
Etymology
Noun
layshaft (plural layshafts)
A subsidiary transmission shaft.
Source: Wiktionary
Lay shaft, or Lay"shaft`, n. (Mach.)
Definition: A secondary shaft, as in a sliding change gear for an
automobile; a cam shaft operated by a two-to-one gear in an internal-
combustion engine. It is generally a shaft moving more or less
independently of the other parts of a machine, as, in some marine
engines, a shaft, driven by a small auxiliary engine, for
independently operating the valves of the main engine to insure
uniform motion.
Source: Webster’s Unabridged Dictionary 1913 Edition