stellar

English "stellar" comes from Latin stēllāris, meaning "of the stars," which was formed from stēlla, "star." That Latin word traces back through Proto-Italic *stērlā to the Proto-Indo-European root *h₂stḗrder, itself built from *h₂eHs- and the agent-forming suffix *-tḗr.

The word entered English directly as a borrowing of the Latin adjective stēllāris, keeping its core sense of "relating to stars." From there it stretched into the more casual, glowing praise we use today — a performance can be "stellar" with no stars in sight.

It shares its Latin root, stēlla, with the astronomical vocabulary built on "stell-," though the facts here don't trace it further into other English words.