Short for: "The mastering of whores."
A typical saying of men from the northern midwestern states (ie: Minnesota and Wisonsin), born in the 20's, 30', or 40's.
Used to describe the act of buying sluts drinks with the intention of engaging in sexual relations with them on weekend nights.
Grandpa: When I was your age, me & George went whore-masting every night.
Grandson: What's "whore-masting"?
Grandpa: The mastering of whores!