boa n.

late 14c., "large snake," from Latin boa, type of large serpent mentioned in Pliny's "Natural History;" a word of unknown origin (in medieval folk etymology the name was associated with Greek bous "ox"). Applied by 1620s to a type of large, non-venomous serpent of the South American tropics that kills by constricting its prey. Extension to "snake-like wrap of fur worn around the throat" is from 1836. The popular name boa constrictor is by 1808 in English (from 1770s in German, 1780s in French).