Thomas Jefferson is credited with being one of the first people to use mammoth as an adjective. While he might not have coined the usage, he was certainly integral to its popularity.
The Mammoth…
Mastodon fossils had been found in the United States, well, before it was the United States. In 1705 some large teeth had been found, which Puritan clergymen attributed to a race of giants destroyed in Noah’s flood.
(Some historians think the ancients made similar assumptions about fossils they may have discovered. Apparently there are little to no references among the ancients about finding fossils, but much about finding the skeletons of heroes and monsters. There is a theory that at least some of the classical myths dealing with giants and monsters were originally inspired by fossil finds. One proposed derivation is that the large hole where the trunk would have attached in mammoth skulls led to the myth of the Cyclops with its one huge eye dead in the center of its forehead.)
In 1799 workers found large bones while digging on a farm in the Hudson River Valley. A number of local people started pulling bones out of the ground and housing them in the granary. Interest in them waned for a year or so, but eventually news spread to the American Philosophical Society and through them to not just yet president Thomas Jefferson.
Jefferson sent his friend Charles Willson Peale, the artist and creator of the first American art and natural science museum, to investigate. He was officially there to draw the fossils, but soon decided to acquire them and the rights to look for the rest. He eventually managed to get nearly a full skeleton, and in 1801 brought it back to his museum and gallery in Philadelphia. He spent months reconstructing it with the aid of naturalist Caspar Wistar.
Years later Jefferson would have William Clark to continue the hunt for mammoth bones in the Hudson River Valley and elsewhere, partially in the hope of finding the parts missing from Peale’s skeleton.
…and the Cheese!
The Cheshire Mammoth Cheese was a gift from the town of Cheshire, CT to Presisdent Jefferson. In a letter Jefferson described it as being 4’ 4 ½” in diameter and 15’ thick and weighing 1230 pounds.
The gift was both instigated and delivered by pastor Elder John Leland as a thank you from the local Baptist community to Jefferson for his stance on religious liberty and sustaining the division between church and state. The cheese was too big to be transported on a wheeled vehicle, so Leland brought it from Cheshire to Washington DC by sleigh.
Jefferson’s election was a tempestuous one, and he was often skewered by the federalist papers. A writer at the Hampshire Gazette derisively took the name of Jefferson’s famous creature and used it as an adjective to emphasize how ridiculous he found the giant cheese and its winding path to DC. Jefferson himself later used the term in a letter he wrote to his son-in-law describing the famous cheese. (note: Jefferson was morally opposed to elected officials accepting gifts, so he in turn made a gift of $200 to the town of Cheshire.)
Magpie's Miscellany 
It was Cheshire, Mass. that made the giant cheese, not Cheshire CT where a mastodon bone was found in 1827 by canal diggers.
Oh, thank you! So much for the books will be more reliable than internet theory 😉
Also intersting since I’d heard most of New England was a poor area for fossilization.