Sapper

Literally, a sapper is one who digs a sap, which is a trench or tunnel. A sapper is a private in the Corps of Royal Engineers, a rank that was first introduced in the British army in 1856. In the US Army, sappers are known as combat engineers and they start with the rank of private. French armies have employed sapeurs since the 16th century and that is the etymology of the word according to the OED. The verb 'to sap' is even older, dating from the late 1500s, and originates from the Italian zappa, meaning spade or spadework, which of course is the tool that sappers use or the work that they do.