Idiom refers to a word, phrase or an expression whose collective meaning differs from their individual (words) meaning.
Drag one’s feet
Meaning: Make unnecessary delay in doing or completing something.
Ex.: The CEO was dragging his feet on the workers’ bonus issue.
Pull someone’s leg
Meaning: To tease, make a fool, or trick someone.
Ex.: Do you really want to help me or are you just pulling my leg?