An arboretum (plural: arboreta) in a narrow sense is a collection of trees only. Related collections include a fruticetum (from the Latin frutex, meaning shrub), and a viticetum, a collection of vines. More commonly, today, an arboretum is a botanical garden containing living collections of woody plants intended at least partly for scientific study. An arboretum specializing in growing conifers is known as a pinetum. Other specialist arboreta include salicetums (willows), populetums, and quercetums (oaks).
The term arboretum was first used in an English publication by John Claudius Loudon in 1833 in The Gardener's Magazine but the concept was already long-established by then.(Wikipedia)