What's in a name? Well, for most anime series, especially those that come from light novels, the general idea or main premise of the series is introduced in its title. One Piece is about Monkey D. Luffy's quest to find the legendary titular treasure; Dragon Ball, despite having developed far beyond, is about the magical wish-granting orbs – also titular. My Girlfriend and My Childhood Friend Fight Too Much is about... well, that.
Some titles are definitely more thought out than others, some are a little less obvious regarding their relationship to the story, and one title from Shounen Jump's Big Three that usually comes up is of course, "BLEACH". Why is the series called that, and how does the name actually connect to the premise and its characters?
Black and White
In BLEACH, the Shinigami are the main faction, and their role is to act as psychopomps for the souls of the dead. They enable the dead to pass over to the in-universe afterlife known as Soul Society, and purge the maligned souls known as Hollows so that they too may pass on. Dressed in their iconic all-black Shihakusho ("Garment of Dead Souls"), they have the ominous appearance that is invoked by the concept of death and psychopomps; however, some of their duties involve doing things that are, at least appearance-wise, not quite so ominous. Bleach, the detergent, removes colour from garments, and this is sometimes in order to prepare them for other processes, or to simply purify the whiteness of the garment which had been discoloured.
Shinigami, when fighting against Hollows, effectively remove the impurities from the soul in question, enabling it to return to the cycle of souls, pass over to the afterlife and live anew there. When a human soul (also known as a "Plus") is sent to Soul Society, their memories of their time in the world of the living are voided; however, there are some special cases that have been able to retain some of their memories from their human life. One such soul is Yuuichi Shibata, the child whose soul was trapped in a parakeet by an evil sentient Hollow known as Shrieker. The Shinigami's dual-role is, in a metaphorical sense, the bleaching of human souls so that they may continue their journey in the greater cycle of souls. It is also noteworthy that two of the Shinigami's greatest enemies – the Arrancar and Hollows led by Sosuke Aizen, and the Quincies – dress themselves in white as a marker of their positionality on the opposite end of what Shinigami are, in different respects.
BLEACH
While the aforementioned concepts make sense for the series, they are not the main reason why the series is aptly named. In fact, author Tite Kubo's initial concept with the series was called "Snipe", and what would be that story's equivalent of the Shinigami and the Gotei 13 would be armed with guns, not swords, with Rukia being the only character armed with a special telltale weapon – a scythe (this design went on to be referenced in the third official BLEACH anime film, BLEACH: Fade to Black). Anyway, the reason for the series' title may not lie with the Shinigami, but with the main character himself. On the cover of the official BLEACH Pilot Chapter (sometimes referred to as BLEACH chapter 00), the prototype of BLEACH, Ichigo's hair is noticeably jet black instead of the orange for which he is now known.
This is extremely important as in the main series, Ichigo Kurosaki's orange hair is incredibly important to his character. His naturally orange hair causes him to stand out among people; and it has been the reason for bullying, as well as the reason why he is constantly treated like a delinquent despite being, for the most part, a pretty stand-up guy. In Japanese media, a mark of delinquency now employed to the point of ruin is that of blonde hair. It is seen as a universal calling card for an individual's abandonment of modesty in favour of standing-out, or even rebellion. The reason why the series is called BLEACH is due to Ichigo's life being consistently made more complicated simply because his hair is naturally orange, and people in his past have been convinced that he bleached his hair to achieve this result (in order to stand out).
Naming Sense
Given Tite Kubo's tendency to have the various elements of his story have various layers of significance, it is of no surprise that the very title of the series is no different. "BLEACH", while being catchy and cool, is also easy to remember because of its jarring and assumed lack of real connection to the story. It is a great name for the series as the protagonist has undergone several kinds of loss, several kinds of rebirth and has found himself built up from the bottom on several occasions. The title relates to the events of the series on various levels while also centering the series' protagonist and in a sense, encapsulating Ichigo Kurosaki's perilous journey from unaware soul to a true agent of overwhelming influence – what the Quincy King Yhwach regards a Special War Power.