Ellipsis of Lady Amherst's pheasant.
"The garden was filled with colorful birds, including a rare amherst that fluttered among the bamboo stalks."
In plain English: Amherst is not a single common word but usually refers to either Amherst College, an American university, or the town of Amherst where it is located.
"The residents of Amherst enjoy their small-town atmosphere and friendly neighbors."
An English surname.
"Professor Amherst taught history at the local university."
The word "amherst" does not come from an ancient combination of words meaning elm and wood; instead, it was borrowed directly into English as the name of a person. The town in Nova Scotia takes its name from Jeffery Amherst, 1st Baron Amherst (1717-1797).