Thinker

wiktionary

ref

From Middle English thinkere, equivalent to think +‎ -er. Compare West Frisian tinker(“thinker”), Dutch denker(“thinker”), German Denker(“thinker”), Danish tænker(“thinker”), Swedish tänkare(“thinker”).

etymonline

ref

thinker (n.)

"one who has cultivated the powers of thought," mid-15c., agent noun from think (v.).