O – Ostentation
An ostentation of peacocks.
It was an odd sensation (ostentation) – she knew there were really no peacocks there, but she kept seeing them in the kitchen.
Ostentation means a showy display of wealth and luxury in an attempt to impress other people. Peacocks are very showy with their colourful tail feathers and proud posture, hence the choice of word "ostentation" as the collective noun for peacock.