Onii-chan combines onii, meaning older brother, with chan, an affectionate honorific used for someone close and familiar. The phrase is a staple of anime and manga dialogue, especially for younger sister characters, and clips of it spread widely through meme soundboards and short video edits. Variants like onii-chan, onii-chan repeat the call for comic effect, while related anime phrases are used the same way in fan edits. Its popularity comes from how quickly a single word conveys a whole character dynamic that anime fans immediately recognise online.