What is the origin of 'sleep tight'?
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Definition of merchant's mark in US English:
merchant's mark
noun
historicalAn emblem or other distinctive figure or device adopted by a merchant and placed on the goods sold by him (in the Middle Ages often used as a quasi-heraldic cognizance, e.g. on seals or monuments).
Origin
Mid 16th century. Compare post-classical Latin signum mercatorium.
