What is rebracketing in linguistics?(1)

Rebracketing is part of the process of language change, and often operates together with sound changes that facilitate the new etymology.

Rebracketing is sometimes used for jocular purposes, for example in English “psychotherapist” can be rebracketed jocularly as “Psycho the rapist”, and “together in trouble” can be rebracketed jocularly as “to get her in trouble”.