What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
= philosophia prima.
Mid 19th century; earliest use found in American Whig Review. From post-classical Latin prima philosophia from classical Latin prīma, feminine of prīmus + philosophia, after ancient Greek ἡ πρώτη ϕιλοσοϕία metaphysics (Aristotle).