To go through the chatterhouse. Between the legs of one or more boys, set apart like an inverted A, who strike, with their hands or caps, the victim as he creeps through. Halliwell (Archaic Dict.) gives chat, a small twig, and chatter, to bruise; also chattocks, refuse wood left in making faggots. Probably, the boys used little twigs or sticks instead of caps or hands. And to go through chatterhouse means to get a trouncing or tunding. The pun between chatterhouse and charterhouse is obvious.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894