Battered

This word has several meanings: the first refers to a type of cooking where something (like chicken or pork) is coated with breadcrumbs and is fried.

The second meaning is when something is bruised or injured through use.

The third meaning implies domestic abuse.

In the context of this poem, the second meaning, that the father’s knuckle is “battered” from work, makes the most sense, though depending on the interpretation, it’s possible that Roethke uses this word to imply that the father is abusive.