Collective nouns for lice include flock, colony, and infestation. A flock is a group of lice that have gathered together, while a colony is a larger group of lice that have formed a community. An infestation is a large number of lice that have invaded an area. The term ‘infestation’ is derived from the word ‘infestare’, which means ‘to invade’. This term was used to describe a large number of lice that had invaded an area.