Rookery today enjoys a healthy outdoor connotation and pertains to natural places where birds and animals gather to perform elaborate rituals involved in reproducing their kind. But rookery has been part of the language since 1792, when it was used as a slang term for “a cluster of mean tenements densely populated by people of the lowest class.” Charles Dickens, in Sketches by Boz, described this grim nineteenth-century London habitat as “wretched houses with broken windows patched with rags and paper . . . ﬁlth everywhere . . . men and women in every variety of scantyanddirtyapparel.”Theslangterm“torook”—tocheatorsteal— evolved from the degrading experience of the slums. Webster’s Dictionary (1913) deﬁned the word as both a breeding place for birds and “a dilapidated building with many rooms and occupants.” With the gradual disappearance of squalid slums in Great Britain, the word became associated almost exclusively with the crowded breeding places of gregarious birds and animals such as herons, penguins, and seals.