There was a ye olde professional baseball team called the Connellsville Cokers. What’s a coker?
Here’s one definition.
Coke was used to produce cast iron from iron ore. It burns hotter and with less smoke than coal.
Connellsville, Pennsylvania, was known for its coal mining and coke production.
And it fits right in with the history of the city that I’m seeing on wiki.
In the context of the OP, it would be someone employed in making coke, a fuel derived from coal.
Coke is to coal as charcoal is to wood. Coal is heated in coke ovens, driving out the more volatile compounds. Toward the end of the age of steam, coke was greatly preferred over coal for railroad use. It had higher energy density, burned hotter, and produced less soot fouling of the boiler flues. You can still see coke ovens along many railroads. They were usually built as a group of perhaps 100 ovens, and they sort of look like giant bee hives. These were usually located near where the coal was mined, so that the bulkier coal didn’t need to be transported as far.
Nobody made a joke about the white foul lines.
And back in those days, you had dudes who had to keep the coke hot by moving air, so you had blowers and… coke suckers.
One of Mad’s best cartoonists:
Some people call him Maurice.