H (エッチ)

The word エッチ refers to anything sexual. This slang comes from the alphabet "H", I am not sure how but some say it comes from the initial of the word "Hentai" (へんたい/変態).

For example: エッチ 小説 means "x-rated novels".

エッチ can also mean "to have sex" or "to make love".

For example: エッチしようか means "want to make love?"