pretty: [OE] In Old English pretty (or prættig, as it was then) meant ‘clever’ in a bad sense – ‘crafty, cunning’. Not until the 15th century had it passed via ‘clever’, ‘skilfully made’, and ‘fine’ to ‘beautiful’. It was a derivative of prætt ‘trick, wile’, which came from a prehistoric West Germanic *pratt- (source also of Dutch part ‘trick’). [pretty etymology, pretty origin, 英语词源]