prewarn

verb

pre·​warn ˌprē-ˈwȯrn 

variants or pre-warn

prewarned or pre-warned; prewarning or pre-warning

transitive verb

: to warn (someone) beforehand : forewarn

… in 1951, the network began to unravel, and two of its members, Donald Maclean and Guy Burgess, prewarned by fellow conspirators, jumped the night ferry to St.-Malo …

—Stephen Koch

Word History

First Known Use

circa 1624, in the meaning defined above