A person who is excessively servile or obsequious; a sycophant or flatterer who debases themselves for favor.
Compound of 'foot' and 'licker,' meaning literally one who licks feet, used metaphorically since at least the 17th century to describe shameless flatterers and yes-men.
Footlicker is delightfully insulting—it paints a vivid, degrading image that's way more cutting than 'sycophant,' which is probably why it survives despite being considered archaic.
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