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Etymology: Previous versions of the OED give the stress as: unˈthinker.
the mind > mental capacity > thought > absence of thought > [noun] > person exhibiting
1837 T. Carlyle I. iv. i. 167 Thinkers and unthinkers,..are spontaneously at their post.
This entry has not yet been fully updated (first published 1926; most recently modified version published online June 2019).