Correct spelling for the English word "Shamp" is [ʃˈamp], [ʃˈamp], [ʃ_ˈa_m_p] (IPA phonetic alphabet).
The word "shamp" is a shortened form of the noun "shampoo" or the verb "shampooing". "Shampoo" itself has an interesting linguistic background. It is derived from the Hindi word "chāmpo", which was a verb meaning "to massage". This term was later adopted into the English language during the colonial era when British travelers encountered Indian traditional hair massage techniques. The word was initially used specifically for the head massage performed with the application of soap or an herbal preparation. Over time, "shampoo" evolved to refer both to the massage and the cleansing process itself. The shortened form "shamp" is likely an informal or colloquial variation of "shampoo".