The related and more common term pansexual was popularized by psychologists in the early 1900s, but the word omnisexual is a more recent variation.

There is some dispute about whether omnisexuality and pansexuality are the same or different. Some have argued that a pansexual person is gender-blind (i.e., they’re attracted to anyone regardless of gender), while an omnisexual person is gender-inclusive, attracted to people of all genders. So, an omnisexual person might say “I like people of every gender,” while a pansexual would answer, “I don’t care about your gender. I like you anyway.” Still, many use the terms interchangeably, including major media outlets like CNN.

Omni- is a Latin-based prefix meaning “all,” while pan- is its Greek counterpart. Omnisexuality appears as early as 1959 in beat poet and journalist Lawrence Lipton’s The Holy Barbarians, with the forms omnisexual and omnisex recorded by the 1970s.

A 1984 text, Sexual Choices: An Introduction to Human Sexuality, described omnisexuality as a state of attraction to all sexes, stating that “some researchers” believe every individual is born omnisexual before they become heterosexual, homosexual, or other sexual orientations.

The early 1990s saw omnisexual further spread, such as a 1991 analysis of poet Walt Whitman by M. Jimmie Killingsworth, who wrote about a “general (omni)sexual character of the Leaves [of Grass].” Whitman has later been described as being omnisexual in the 2010s, with The Atlantic, for instance, noting that his poetry expresses sexuality for all genders, sometimes even the sea or Earth.

The wide arms of the internet latched onto the term by the 21st century, and by the early 2000s, omnisexual was a common term used on internet message boards. It was further boosted by greater visibility of nontraditional, non-binary sexual orientations and gender identities in the 2010s. In 2018, singer Janelle Monáe came out as pansexual (as did Miley Cyrus in 2015), which many popular articles discussed alongside omnisexuality.

The character Jack Harkness on Dr.Who has been identified as omnisexual, as has the Marvel comic book and movie character Deadpool.

Many sexuality researchers classify both omnisexual and pansexual as terms that fall under the more commonly known bisexual, with the latter acting as an umbrella word but the former giving people the ability to better explain the nuance of their identity.