Put to sleep

The phrase ‘put to sleep’ is suggestive of a quiet peaceful demise, such that a vet might provide for an dying animal in order to forestall prolonged suffering. It’s the kind of euphemism that might be spoken to a child when their beloved pet had to be killed.

The earliest example of the expression that I’ve found in print doesn’t quite live up to that ethical standard. It is a story of a woman who wanted to have her, presumably healthy, pet dog killed in order for it to be buried with her. It comes from the English newspaper The Western Gazette, December 1934:

That her dog Punch should be painlessly put to sleep buried with her was a request in the will of Mrs. Henrietta Elizabeth Lascelles, of Benson Hill-parade, Herne Bay.