zoo:  Greek zóion meant ‘animal’ (it came from the Indo-European base *gwei-, which also lies behind English biology, quick, and vital). From it was formed modern Latin zōologia ‘study of animals’, which English adapted as zoology . Zoological was derived from this in the 19th century, and when the Zoological Society of London opened their exhibition of live wild animals in Regent’s Park in 1829, they called it the Zoological Gardens. This was soon abbreviated to ‘the Zoological’, and by the mid 1840s it had shrunk further to zoo. => biology, quick, vital
c. 1847, short for Zoological Gardens of the London Zoological Society, established 1828 in Regent's Park to house the society's collection of wild animals. The first three letters taken as one syllable. "From a mere vulgarism, this corruption has passed into wide colloquial use" [Century Dictionary]. Slang meaning "crowded and chaotic place" first recorded 1935.