Literally "one who stuffs". Originally referred to longshoremen or cargo workers in the maritime industry since before the industrial revolution. Nowadays in common usage it describes someone who swears profusely or who garners a lot of poon tang.
The Stevedores unloaded the ship quickly and without incident.
Man, when Chris drinks he really has a mouth like a Stevedore
Geez, Jon disappeared three times with three different girls last night at the party, he's a real modern age stevedore!