It's Not Porn, It's an Index
This isn't dirty, we swear.
The titles of these tropes seem like they belong in Nudity Tropes
or Sex Tropes
, but they aren't (no, Rule 34
doesn't make them so).
Often it's because the title seems that way as a joke (especially Just for Pun
titles), and often because the name uses a word that has multiple meanings where one is well known to be about sex. For others, it's a case where the object of affection is given the same amount of drool and adoration as actual porn might be.