Is it ensure, insure, or assure?
by 1974 in sense of "devotee of the rock music band the Grateful Dead;" earlier (with lower-case) "one who rides for free on the railroads" (1866), and "non-paying spectator" (1841).
: a deadhead cab/ deadhead freight train
: I'll deadhead your hack back to the garage
A devotee of the rock-and-roll group the Grateful Dead: Tipper Gore, Deadhead and wife of Vice President Al Gore (1970s+)