Traditional celebrations of the arrival of Summer on May Day had a rich cast of characters, not least the mysterious figure of the sinister Jack-in-the-Green, who wore a large, foliage-covered, garland-like framework, usually pyramidal or conical in shape, covering the body from head to foot. The costume was a development of the 16C & 17C custom of decorating homes (and people) with garlands of flowers & leaves for the May Day celebration.
After becoming a source of competition between Britain's Works Guilds, the garlands became increasingly elaborate, finally covering the entire man. This figure resulting from extreme garlanding became known as Jack-in-the-Green. For some reason the figure became particularly associated with chimney sweeps.