knap of the case, the, n. — Green’s Dictionary of Slang

knap of the case, the n.

[? SE knap, the crest or summit of a hill, but OED, which includes it as a derivative, notes ‘doubtfully placed here’ + case n.³ (1)]

(UK Und.) the head of the house.

1552

G. Walker Detection of Vyle and Detestable Use of Dice Play 29: The knapp of the case, the goodman of the house calleth secretly unto him the third person.