Applying lubricating oil or grease to machinery or moving parts to help them work smoothly; or offering bribes to officials.
From 'grease' (oily substance) plus '-ing'. Literal sense from medieval times; corruption metaphor emerged in the 1800s.
The phrase 'greasing palms' for bribery reflects how lubricating something makes it move easier—in corruption, offering bribes 'lubricates' official decisions in the briber's favor.
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