A quirky, silly and/or stupid, socially inept person, or one who is out of touch with contemporary trends. Often confused with nerd and geek, but does not imply the same level of intelligence.
A penis.
nerdbrain
noun
A nerd; a socially awkward brainy person.
How often have the words dork and nerdbrain occurred in a corpus of books? (source: Google Ngram Viewer )