Ephraim was a tardigrade whose reproduction was the subject of the film The Tardigrade in Space.
According to the film, after laying her eggs aboard the USS Enterprise, she witnessed various events in the starship's history, including a discussion between James T. Kirk, Leonard McCoy, and Khan Noonien Singh. She encountered a DOT-7 repair drone named Dot, which pursued her until 2285, at which point Dot realized Ephraim's purpose aboard the ship, and switched over to helping her. (ST: "Ephraim and Dot")
"Ephaim" in the title reveal trailer
Ephraim was also the name of an early conception of Ripper, which would have been a tardigrade crewmember and Stamets' boss. This character was named after the discoverer of the tardigrade, Johann August Ephraim Goeze. [3]
The novel Dead Endless features a tardigrade named Ephraim, which the book's author, Dave Galanter, suggested to not only be the same tardigrade that appears in "Ephraim and Dot", but also Ripper. [4]