Gullivers Travels by Part 4 Chapter 1 Page 16

I could frequently distinguish the word Yahoo, which was repeated by each of them several times: and although it was impossible for me to conjecture what it meant, yet while the two horses were busy in conversation, I endeavoured to practise this word upon my tongue; and as soon as they were silent, I boldly pronounced Yahoo in a loud voice, imitating at the same time, as near as I could, the neighing of a horse; at which they were both visibly surprised; and the gray repeated the same word twice, as if he meant to teach me the right accent; wherein I spoke after him as well as I could, and found myself perceivably to improve every time, though very far from any degree of perfection. Then the bay tried me with a second word, much harder to be pronounced; but reducing it to the English orthography, may be spelt thus, Houyhnhnm. I did not succeed in this so