Ecchi

Ecchi (エッチ), also romanized as etchi, is derived from a Japanese word meaning "erotic", "lewd", "sexy", or "lascivious" when used as an adjective, or sexual intercourse when used as a noun.

Etymology
The purported origin of the Japanese word is the Latin alphabet letter "H". The most common theory states that it derives from the first character of the word hentai (変態), and indeed the two words have similar meanings.

Japanese usage
The origin of the term ecchi is uncertain. Ecchi in Japanese is attached to the Japanese pronunciation of the Roman letter "H" which is the first letter in the Japanese word "Hentai", which may be backronym.

The word sekkusu is also used in Japan for sex, and Japanese native words for sex (such as 性交 seikō) are often replaced by words of foreign origin such as sekkusu or neologisms such as ecchi. The nuance of ecchi varies with context, but in general the word itself is comparable to the English words "naughty" or "dirty" (when used as an adjective). The prefix "H-" is sometimes used to refer to pornographic genres: H-anime, H-manga, etc.