Kurehat is a Punjabi word which has two roots - Ku meaning opposite or negation and rehta which mean 'code of conduct'. So the word Kurehta means conduct from which to refrain or keep away from.
It is said that when Guru Gobind Singh first initialled the five Sikhs (Khalsa) in 1699 he mentioned the four Kurehta (the four prohibitions) to them after they had taken Amrit (baptism ceremony with water) at Vaisakhi 1699. The Guru asked the five Panj Piare (beloved of the Guru) to refrain from the four Kurehtas; namely,
1. Cutting or trimming of hair or Kesh,
2. Fornication or adultery,
3. Halal meat or flesh of animal slaughtered in a slow and painful manner, (some say all meat is banned - the Guru is believed to have used the word - "Kuthha")
4. Use of tobacco and intoxication drug.