Term coined by the lead singer of The Small Faces to describe the feeling when the amphetamines kick in. Became the name of probably the original progressive rock act, formed of Keith Emerson on organ, Blinkey Davidson on drums, Lee Jackson on bass, and Dave O'list on guitar: the forerunner of Emerson, Lake and Palmer (ELP).
Famed for Keith Emerson's stage performances involving serious organ abuse (imagine if Hendrix played the Hammond), throwing it around on stage, setting fire to it, sticking knives in it etc.