Traditionally, the one who discovers a Star can name it.

So why did astronomers name this huge star that dates to the dawning of the Universe "Earendil"

Back in March 2022, the Hubble Space Telescope team announced the observation of the furthest ever star detected. That star, nicknamed Earendel, was detected from light that look 12.9 billion years to reach Earth, when the universe was only 7 percent of its current age.

 This ancient star breaks the record of the previous most-distant star by several billion years. The discovery of Earendel was made using data collected by Hubble's RELICS (Reionization Lensing Cluster Survey) program, led by astronomer Dan Coe from the Space Telescope Science Institute (STScI). The paper on the find was published in Nature.

The star gives a view of the very early universe, when the stars were generated from the early matter of the big bang: a star from the morning of the universe.

More here at SkyAndTelescope.

EARENDEL: AN EARLY STAR Based on Earendel’s brightness, the group estimates that it’s massive, containing the equivalent of tens or even hundreds of solar masses, with few elements other than hydrogen and helium. Given the age of the universe it resides in, Earendel is not likely to be one of the very first stars, known as Population III, but at its great mass, it’s nevertheless an early fuser of new heavy elements.

“Knowing that massive stars were present that early on in the universe is an important confirmation of what many of us have predicted and in fact used as assumptions in the work with old Milky Way stars,” says Anna Frebel (MIT), who was not involved in the study. For Frebel, who studies ancient nearby stars for clues to stellar evolution in the infant universe, the discovery is a fantastic find. “Early massive stars must have produced the first elements and driven chemical evolution, so having observations at hand that support this notion is wonderful.”

Earendil, as Tolkien fans know, is an important character in the Simarilion.... but originally the word Earendil was an ancient name for the Morning Star, and the word Earendil in an Anglo Saxo Poem Crist was the original inspiration for Tolkien's mythology. 

TolkienGateway:

While Eärendil is a Quenya name inside the legendarium, Tolkien created the name based on Anglo-Saxon éarendel. He says that he was struck by the "great beauty" of the name as early as 1913, which he perceived as "entirely coherent with the normal style of A-S, but euphonic to a peculiar degree in that pleasing but not 'delectable' language."...

The Old Norse together with the Anglo-Saxon evidence point to an astronomical myth, the name referring to a star, or a group of stars, and the Anglo-Saxon in particular points to the Morning Star as the herald of the rising Sun (in Crist christianized to refer to John the Baptist). Tolkien was particularly inspired by the lines in Christ, which became the title of his first poem about Eärendel:

éala éarendel engla beorhtast / ofer middangeard monnum sended

"Hail Earendel, brightest of angels / sent over Middle-earth to men."