The importance of being ernest?

Question

Can someone explain the pun Gwendolyn makes?

Cecily: When I see a spade, I call it a spade.
Gwendolyn: I am glad to say I have never seen a spade. It is obvious that our social spheres have been widely different.

Answer 1

could be a reference to gardening/manual labor, or the racial slur... given the "social spheres" I'm guessing Cecily meant the gardening, and Gwendolyn meant the slur