Sea-change

Describes a fundamental, major or considerable change and dates from the 16th century, coined by Shakespeare in The Tempest (1610) where Shakespeare describes a mystical change to the body of Ferdinand’s father as a 'sea change' in Act I, Scene II. This magical transformation was caused by the sea, in Shakespeare’s words, 'a sea change'. Quite how this poetic concept was then absorbed into the language to denote a considerable or fundamental change remains a mystery