oil peddler
Historical occupation; a person who sold oil, often door-to-door. Now mostly encountered in historical or literary contexts.
In the Edo period, oil peddlers went around towns.
Idiomatic use derived from the image of an oil peddler who would stop and chat, wasting time. Used to describe someone who is loafing or not working diligently.
That guy is always loafing around.
Compound of 油 (oil) and 売り (selling). The literal sense refers to an oil peddler. The idiomatic sense 'lazy person' likely comes from the stereotype of oil peddlers idly chatting with customers instead of working efficiently.