I think that the last time I ran across "haecceitas" in a literary context was in an essay by Randall Jarrell. My guess is that he was referring to William Carlos Williams. In that case, Jarrell meant writing that tried to engage each thing as it is, not as part of a larger class.
Yepp the "academic" flavour of it is ... slightly different (& less relevant imho to parent thread) ... than the pop-cultural one, should have stressed that it exists ntheless. Thank you for providing more context for "context elision" :)!
