For uncircumcised males, stimulation of the penis in this way comes from the pumping of the foreskin, in which the foreskin is held and slid up and down over the glans, which depending on foreskin length, is completely or partially covered and then uncovered in a rapid motion. The scenario is a genre of erotica, which on the internet is sometimes abbreviated milf xxx to CMNF, and may involve sexual and nonsexual erotic scenarios. Originating in Japan in the 1980s, the genre subsequently spread to North America and Europe, and crossed over into gay pornography. Since at least 1973, it has also been used to refer to a sexually attractive young woman. Individuals are also sometimes abbreviated when referred to in writing, so a dominant person may be referred to as a Dom for a man, and a Domme for a woman. BDSM actions can often take place during a specific period of time agreed to by both parties, referred to as play, a scene or a session. Watersports pornography features sexual activities involving urine, such as golden showers. Many men who like trans partners of any variety, known as tranny chasers, do not necessarily identify as gay themselves. There is also some evidence that pornography can be used to treat voyeurism. Advocates of RACK argue that SSC can hamper discussion of risk because no activity is truly safe, and that discussion of even low-risk possibilities is necessary for truly informed consent. Several hundred exclusively pegging films hentai porn were produced, as well as twice as many bisexual and straight films with strap-on scenes. As in B/D, the declaration of the Top/Bottom may be required, though sadomasochists may also play without any Power Exchange at all, with both partners equally in control of the play. This category also includes pornographic hot gay sex home movies. Since the 1980s, many practitioners and organizations have adopted the motto safe, sane and consensual, commonly abbreviated as SSC, which means that everything is based on safe activities, that all participants be of sufficiently sound/sane mind to consent, and that all participants do consent.