Adrian,
   "chantage n. [Fr.] blackmail"
existe in mi Webster's New Universal Unabridged Dictionary.

Cerca vostre Oxford Dictionary (complete).

Assi io ha

Fr.   chantage
Sp.   chantaje
Port. chantagem
Russ. shantazh
Eng.  blackmail, chantage

Obviemente, le parola "chantage" in anglese es un parola "estranier" e
possibilemente es usate in novellas detective super detectivos francese.

Stan Mulaik