Another note on the ambiguity of compound nouns, inspired by a story on the radio about a dog that performed a rescue, a rescue dog with dog functioning like the subject of the verb rescue — that is, with the dog as agent in the rescuing event. But then there’s rescue dog with dog functioning like the object of the verb rescue — that is, with the dog as patient in the rescuing event. Call these the “agent reading” and the “patient reading”, respectively. The agent reading goes back at least to 1901, but the patient reading is much more recent; the OED‘s first cite is from 1980.
OED3 (March 2010) has the two readings folded together, awkwardly, in a single subentry:
rescue dog n. (a) a dog trained to aid in rescue operations; (b) a dog that has been rescued from abuse, neglect, etc.
with two cites for (a):
1901 Strand Mag. Dec. 716/1 A great St Bernard, the most celebrated of all the rescue dogs that have worked in the hospice on Mount Bernard. [no doubt earlier cites will be found]
1992 1001 Images of Dogs ii. 32 In addition to being an excellent working sheepdog it [sc. the Appenzell, or Alpine Shepherd Dog] is also used as a ski patrol dog, security dog and rescue dog.
interleaved with two for (b):
1980 P. G. Burnham Playtraining Your Dog i. 25 If you are involved in dog rescue work, a rescue dog can be made much more suitable for adoption after two months of letting you practice on him in the Novice class.
2003 J. Katz New Work of Dogs i. 9 It seems that every other dog here is a rescue dog, ‘probably abused’, their owners often say.
On the agent reading, rescue dog is parallel to ski patrol dog and security dog (as in the 1992 cite), seeing-eye dog, herding dog, assistance dog, watch dog, etc. and even companion dog. And it occurs in the technical label search and rescue dog:
The use of dogs in search and rescue (SAR) is a valuable component in wilderness tracking, natural disasters, mass casualty events, and in locating missing people. Dedicated handlers and well-trained dogs are required for the use of dogs to be effective in search efforts. Search and rescue dogs are typically worked by a small team on foot, but can be worked from horseback. (link)
There’s even a Disney animated feature (from 1947) with the title Rescue Dog. From IMDB:
The snow covered mountains; but not to worry, rescue dog Pluto is on duty. Actually, given that he barely keeps himself safe, maybe you should worry. A playful seal keeps stealing his cask of grog.
On the patient reading, rescue dog is parallel to rescue cat, rescue horse, etc. — all of these more recent than rescue dog, which the OED identifies as the model for the set.
It’s possible that there are rescue dogs (on the patient reading) that have been trained to work as rescue dogs (on the agent reading). They would be rescue dog rescue dogs.