Definition: a mysterious creature with human or apelike characteristics reported to exist in the high Himalayas
Abominable snowman makes an appearance in Charles Howard-Bury's chronicle of his Mount Everest expedition entitled Mount Everest: The Reconnaissance, 1921 (published in 1922):
We were able to pick out tracks of hares and foxes, but one that at first looked like a human foot puzzled us considerably. Our coolies at once jumped to the conclusion that this must be "The Wild Man of the Snows," to which they gave the name of Metohkangmi, "the abominable snow man" who interested the newspapers so much.
Journalist Henry Newman, who interviewed the returning members of the expedition, mistranslated the Tibetan name—metoh kangmi, which roughly means "filthy snowman"—for the suspected yeti as "abominable snowman" in his reporting. (Note that Howard-Bury used the misinterpretation in his book.) Newman admits this in a letter to The Times (London) in 1937:
When I asked him what name was applied to these men, he said "Metoh Kangmi." Kangmi means "snow-men" and the word metoh I translated as "abominable." The whole story seemed a joyous creation, so I sent it to one or two newspapers. It was seized upon…. Later, I was told by a Tibetan expert that I had not quite got the force of the word metoh. It did not mean abominable quite so much as 'filthy' and 'disgusting,' somebody dressed in rags.
There is no etymological mysteriousness to abominable snowman: abominable occurs in Middle English as a borrowing from Anglo-French, which is related to Latin abōminārī, "to detest"; snow is from an Old English word, snāw, of the same meaning; man is from Old English mon, "human being." People have been making human figures, in some form or another, out of masses of snow well before the 19th century, but it wasn't until then that they were identified as snowmen