Why did the boss refer whisky as medicine?

The boss feels sorry for the frail and nervous Mr. Woodfield so he pulls out the whisky. He winks and pulls out a bottle of whisky from a locked drawer in his desk. Mr. Woodifield is shocked at the sight of the whiskey and almost tears up—his wife and daughters don't let him have any whiskey at home. The boss replies that they know more than the ladies. He serves up a tumbler of whiskey to Mr. Woodifield, telling him that it will do him good: it's "medicine".