Cold shoulder – meaning to deliberately ignore somebody.
The first written record we have of the phrase is by Sir Walter Scott who wrote:
“Ye may mind that the Countess’s dislike did na gang farther at first than just shewing o’ the cauld shouther”
Where ‘Cauld shouther’ was local dialect for cold shoulder. The phrase was undoubtedly used before this record though and stems from the idea of providing an unwanted guest with a cold shoulder of mutton rather than a cooked meal – which was the customary way to receive guests at the time. The cold meat would take less time to prepare and thus mean less time the guest would stay it would also convey to the unwanted visitor that they weren’t welcome to stay.