pot calling the kettle black

Etymology:

• There are two interpretations of this phrase, though some sources give only the first interpretation.
• In the first interpretation, it refers to the fact that both cast-iron pots' and kettles' bottoms turn equally black when hung over a fire, and thus the pot is accusing the kettle of a fault it shares.
• In the second, subtler interpretation, the pot is sooty, while the kettle is clean and shiny, and hence when the pot accuses the kettle of being black, it is the pot’s own sooty reflection that it sees: the pot accuses the kettle of a fault that only the pot has.