different between unthink vs unthank

English

Etymology

un- +? think

Verb

unthink (third-person singular simple present unthinks, present participle unthinking, simple past and past participle unthought)

1. (transitive, intransitive) To undo the process of thinking.
   • 1930, G. K. Chesterton, The Resurrection of Rome

     They at least had the immense and mighty imagination of which I speak; they could unthink the past. They could uncreate the Fall. With a reverence which moderns might think impudence, they could uncreate the Creation.

   • 2006, Kirsten Shepherd-Barr, Science on Stage: From Doctor Faustus to Copenhagen

     In An Experiment with an Air-Pump, characters repeatedly assert that "once you've thought something, you can't unthink it, can you?"

See also

• unring

English

Etymology 1

From Middle English unthank, from Old English unþanc (“displeasure, anger, ill-will”), from Proto-Germanic *unþankaz, equivalent to un- +? thank. Cognate with West Frisian ontank, Dutch ondank, German Undank, Danish utak.

Noun

unthank (uncountable)

1. Lack or absence of thanks or thankfulness; thanklessness; unthankfulness; ill-will.
   • 2000, Francis G. Snyder, The Europeanisation of Law:

     It is always by this unthank that things are given to the observer that we pretend to have access to the truth of the word.

2. Harm; injury; misfortune.

   • Unthank come on his hand that bound him so.

Etymology 2

From un- +? thank.

Verb

unthank (third-person singular simple present unthanks, present participle unthanking, simple past and past participle unthanked)

1. (transitive) To recant; unsay, as what has been said by way of acknowledgement.
2. (transitive) To undo or retract one's thankfulness; negate, cancel, or revoke one's thanks.