Bleach is called “bleach” because the word originally means a substance or process that whitens or removes color, and that idea of “whitening/cleansing” is exactly what bleach (the chemical) does and what inspired the manga’s title as well.

The everyday word “bleach”

In normal English, “bleach” is the generic name for any chemical used to remove color from things like fabric, paper, or fibers, or to whiten and disinfect them.

These chemicals are called “bleaches” because they “bleach out” color: they react with colored molecules (pigments) and turn them into colorless ones, so the material looks white or much lighter.

Why the chemical got that name

Historically, people noticed that certain substances or even sunlight could make cloth paler or white, so the process was called “bleaching,” and the agents that did it became known as “bleach.”

Chlorine-based compounds like sodium hypochlorite and calcium hypochlorite became the most common bleaches, especially for laundry and cleaning, so “bleach” in everyday speech now often means a chlorine-based whitening/disinfecting liquid.

The anime/manga title angle

For Tite Kubo’s manga/anime Bleach , the title plays on this same idea.

Kubo reportedly first considered “Black” and then “White” as titles, focusing on the black robes of the Soul Reapers and the black‑vs‑white visual contrast, but ended on “Bleach” as a twist: as if the black clothes or the world itself had been “bleached,” and also as a metaphor for purifying corrupted souls.

Fans also discuss links to cleansing/purification and even to Nirvana’s album “Bleach,” but the main idea is still that visual and thematic “bleaching” from black to white.

TL;DR: It’s called “bleach” because the original meaning is “something that whitens or removes color,” and the word stuck both for the cleaning chemical and, metaphorically, for the manga’s title about black‑clad soul reapers and purification.

Information gathered from public forums or data available on the internet and portrayed here.