Where does the expression “Darby and Joan” come from and What does Darby and Joan mean?

Darby and Joan is typification of marital contentment.

Names and allusion are assumed to be from a set of verses appearing in The Gentleman’s Magazine in 1735 under the title, “The Joys of Love Never Forgot: a song.”

The author was presumably Henry Woodfall, though that is not certain.

The third stanza reads:

Old Darby, with Joan by his side,
You’ve often regarded with wonder:
He’s dropsical, she is sore-eyed,
Yet they’re never happy asunder.