'Stellar' is Latin for 'of the stars' — from 'stella.' The same PIE root gave English 'star' and Greek 'aster.'
Relating to stars; exceptionally good or outstanding.
From Late Latin 'stellāris' (of or pertaining to the stars), from Latin 'stēlla' (star). The Latin form contracts from older *sterla, attested in archaic inscriptions, from PIE *h₂stḗr (star) — the same ancient root that spread across every major Indo-European branch. Greek 'astḗr' (star) gave English 'astronomy,' 'asteroid,'
English has two words from the same PIE root *h₂stḗr (star) — the native Germanic 'star' (via Old English 'steorra') and the Latin-derived 'stellar' (via 'stēlla'). The word 'disaster' also descends from this root: Italian 'disastro' meant 'ill-starred,' from 'dis-' (bad) and 'astro' (star).