fout(re) > hoot(er)

[Rudolph C Troike]

Some plausibility is added to this derivation by the fact that [f] > [h]
is a well-known sound change in Romance (filio: hijo, ferrocarril:
hierro, to cite Spanish examples). As Chomsky and Halle pointed out, the
acoustic similarities of labials and velars makes them subject to
interchange (cf. the history of English /x/ in "laugh"). The change could
have occurred in a regional variety of French (Norman French?) or in the
process of transmission from French to English.

        Rudy