Meaning

noun handsome East Indian evergreen tree often planted as an ornamental for its fragrant white flowers that yield a perfume; source of very heavy hardwood used for railroad ties

noun exceptionally tough or hard wood of any of a number of ironwood trees

noun a small slow-growing deciduous tree of northern Iran having a low domed shape

originFrom iron + wood, because of its toughness.

Etymology from Wiktionary, CC BY-SA 3.0