Each trade can have esoteric words. However, where I come from...shoring is used as in the excavation of a trench...to shore up the sides.
Lagging is used as in pipe insulatiopn...to lag the pipe with fiberglass insulation.
Others may have a different take?
Shoring is the general term for any system that retains earth.
Lagging is usually part of a system of soldier pile and lagging. Basically the lagging is boards that are slid in between piles to retain earth. It is usually temporary.
