When and how did "pretty" enter English as an intensifying adverb?
Solution 1:
The OED’s earliest citations for the word as an adjective are from the Old English period, when it meant ‘cunning, crafty’ and subsequently ‘clever, skilful, able’. It was only in the fifteenth century that it came to have meanings associated with pleasing appearance.
The earliest citation for its use as an adverb meaning ‘to a considerable extent; fairly, moderately; rather, quite’ is from 1565.