I've heard my granny cracketc. In that region, Dandy is dim. of Andrew. In vogue in London c.1813-19. His fem. counterpart was a dandizette (1821) with Fr.-type ending. The adjective dandy first recorded 1792; very popular c.1880-1900.
O' sixty twa years back
When there were sic a stock of Dandies O
"The investigation of human eugenics, that is, of the conditions under which men of a high type are produced." [Galton, "Human Faculty," 1883]