What does the expression “love me, love my dog” mean and Where does it originate?

The expression “love me, love my dog” means whatever my faults, if you love me you must put up with them.

Regrettably, sometimes one’s dearest friend or son or daughter construes this saying literally and thinks himself or herself quite at liberty, because of that friendship, to bring the hugest and smelliest Saint Bernard or flea-bitten pooch, shedding hair on rug or couch, into one’s living-room.

Perhaps some maiden fair did say it in a literal way to her gallant in the days when knighthood was in flower, but it is certainly not so meant nowadays.

It is very old.

Apperson found it in the writings (Latin) of Saint Bernard of Clairvaux (twelfth century) : Qui me amat, amat et canem meum, and it occurs in the works of various English writers of the fifteenth and sixteenth centuries.