At Language Log, commenter “anon” (who I'd guess is British) says:
Many years ago, some Army combat engineers tried to teach dogs to sniff out explosives. They taught the dogs to bark once for a land mine, twice for an unexploded bomb, and so forth. Unfortunately, when the dogs encountered explosives for which they had not been taught barking and growling patterns, the dogs ignored the explosives, and some of the dogs and their trainers were blown to bits.
The engineers concluded that the dogs' ability to detect explosives depended on the words for explosives in the dogs' language.
This is called the Sapper-Woof hypothesis.