Yaoi derives from two sources; in the early 1970s, shōjo manga magazines published tanbi (aesthetic) stories, also known as shōnen ai (boy love), featuring platonic relationships between young boys.
The other influence began in the dōjinshi (fan fiction) markets of Japan in the late 1970s as yaoi, a sexualized parody of popular shōnen manga and anime stories.
Zanghellini notes that illustrations of anal sex almost always position the characters to face each other, rather than in the 'doggy style.' Zanghellini also notes that the uke rarely fellates the seme, but instead receives the sexual and romantic attentions of the seme.
The possibility of switching roles is often a source of playful teasing and sexual excitement for the characters, indicating an interest among many genre authors in exploring the "performative nature" of the roles.
By the end of the 1970s, magazines devoted to the nascent genre started to appear, and in the 1990s the term boys' love or BL would be invented and would become the dominant term used for the genre in Japan.
Although yaoi derives from girl's and women's manga and still targets the shōjo and josei demographics, it is currently considered a separate category.
In the late 1970s, shōjo magazines devoted to the new genre began to appear; and, in the 1990s, the term boys' love or BL was invented for the genre, which replaced earlier terms such as tanbi, shōnen ai and juné in Japanese usage.
In Japan, the term yaoi continues to refer mainly to parody dōjinshi; among Western fans, however, yaoi is used as a generic term for female-oriented manga, anime, dating sims, novels and fan fiction works featuring idealized gay male relationships.
In this case, yaoi is used to describe titles that primarily feature sexually explicit themes and sex scenes, while shōnen-ai is used to describe titles that focus primarily on romance and omit explicit sexual content, although sexual acts may be implied.
and is used in Japanese gay slang to mean the receptive partner ("bottom") in anal sex.
The use of yaoi to denote those works with explicit scenes sometimes clashes with use of the word to describe the genre as a whole, creating confusion between Japanese and Western writers or between Western fans who insist on proper usage of the Japanese terms and those who use the Westernized versions.