Tender
Tender turns up in 2 fields: refractories, railroad. Here is what it means to the people in each one.
Tender in refractories
Laborer who supplies brick, mortar and castable to refractory masons and keeps the job moving.
Short for mason tender: the crew member who stocks brick at the mason's elbow, mixes mortar and castable, runs the saw, handles tear-out debris and moves scaffolding. On a refractory reline the tenders often outnumber the masons, and their pace sets the pace of the whole job. Many brickies start out as tenders.
"Masons are standing around waiting on brick, get another tender on the hoist."
Tender in railroad
A specialized railcar coupled directly behind a steam locomotive to carry its fuel and water.
A heavy-duty trailing vehicle permanently coupled to a steam locomotive, designed to hold the massive quantities of coal, oil, and water required to generate steam. It essentially functions as a mobile fuel bunker and water reservoir. The size of the tender dictates the locomotive's operating range before it must stop at a water column or coaling tower.
"The fireman spent an hour shoveling coal from the tender to get the boiler pressure up."