The band completed the Scandinavian tour as The New Yardbirds. One account of the band's naming, which has become almost legendary, has it that Keith Moon and John Entwistle suggested that a possible supergroup containing themselves, Jimmy Page, and Jeff Beck would go down like a lead balloon, a term Entwistle used to describe a bad gig. The group deliberately dropped the 'a' in Lead at the suggestion of their manager, Peter Grant, to prevent "thick Americans" from pronouncing it as "leed".

-From Wikipedia