[mdp2021]

('thunk': «from an 1876 glossary of words in the mid-Yorkshire dialect in Britain», presumably jocular.

Used by Joyce: “I thunk I told you” (Finnegans Wake); “Have a good old thunk.” (Ulysses)

Does not come, as one may suppose, from a jocular integration from the area of the onomatopeic "thunk", which is 1952. Interesting. Considered in grammarphobia.com )

[cryptonector]

It's a purposeful misspelling of "thought". It's fun to use it once in a while.