Optimist

google

ref

mid 18th century: from French optimisme, from Latin optimum ‘best thing’ (see optimum).

wiktionary

ref

From French optimiste, from Latin optimus(“best”).

etymonline

ref

optimist (n.)

1759, "one who believes in metaphysical optimism," from French optimiste (1752); see optimism + -ist. Meaning "person of a hopeful disposition" is recorded by 1766.