McCall would not walk up to the man and demand "codeword." A codeword in the military is the name of an operation, such as Operation Desert Shield / Desert Storm. The interchange between the two would have been a challenge and password: he should have challenged her by saying "arachnoid" and she should have given the password by saying "mahogany." Done correctly, he would say something like, "Did you see an arachnoid in the truck on the road?" and she would have responded with something like, "I saw a mahogany desk on the flightline." This is so that anyone eavesdropping cannot figure out precisely which words are the challenge and password. [FYI: "Arachnoid" is not a typical challenge or password; "spider" or "scorpion" is far more likely.]
Coordinates 48°59'15. 0"N 1°55'02.0"W are in France, but not on land. This location is northwest of the Normandy Coast and southeast of Jersey Island in the English Channel.