"Hambletonian" That word takes me back to age ten, when I devoured Marguerite Henry's fiction about horses. I must have encountered the word in the book 'Born to Trot.' I never knew the first Hambletonian was a horse.
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The Hambletonian Stakes is a major American harness race for three-year-old trotting horses, named in honor of Hambletonian 10, a foundation sire of the Standardbred horse breed, also known as the "Father of the American Trotter."   -- from wikipedia

Henryp, thanks for the info about betting in the olden days. It certainly sheds light on how the impoverished noble families of present-day novels got that way.
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In the 1794 version which Reinhard linked above, the two owners (Squire Mirvin and Sir Rafe Gore) make a huge wager, but the public bets also.

   The time being come and the cattle [horses] led out
   the people came flocking from east, west and south.
   To beat all the sportsmen I vow and declare
   they'd enter their money all on the grey mare.

It's funny how some things persist. 250 years later, the grey mare is still grey.