incognitum

Borrowed from Latin incognitum (“unknown”). Coined by William Hunter.

incognitum (plural incognita)

1. (archaic) An American mammoth or mastodon, especially when presumed extant.
   • 2014, Elizabeth Kolbert, chapter 2, in The Sixth Extinction: An Unnatural History, Henry Holt and Company:

     When, as president, he dispatched Meriwether Lewis and William Clark to the Northwest, Jefferson hoped that they would come upon live incognita roaming its forests.

incognitum

1. inflection of incognitus:
   1. nominative/accusative/vocative neuter singular
   2. accusative masculine singular