Late 18th century; earliest use found in John Lightfoot (1735–1788), Church of England clergyman and naturalist. From scientific Latin perichaetium (Linnaeus Genera Plantarum (ed. 5, 1754) 487) from ancient Greek περι- + χαίτη long hair, as of a mane, leaves, foliage, in modern use taken also in sense ‘bristle’ + scientific Latin -ium.