What does 死神 Shinigami mean?

Shinigami joins 死 (shi), death, with 神 (kami), a god or spirit. The usual English rendering is god of death, and the more useful correction on this page is that the figure is not ancient.

The characters, and why god oversells it

死 is death, plainly. 神 is the difficulty. English translates it as god, which imports a great deal of weight the Japanese word does not carry: kami covers deities, but also local spirits, natural forces, remarkable objects and the dead, across an enormous range of scale and importance.

A kami can be the presence in a particular waterfall. Rendering the compound as god of death produces something singular and cosmic, where death spirit is nearer and less grand.

It is roughly as old as the steam engine

This is the part most pages omit. The word does not appear in classical Japanese literature. Its first known uses come from the Edo period, in puppet theatre and popular fiction of the eighteenth and nineteenth centuries, where it attaches to spirits that draw people toward death, including the double suicides that were a staple of the stage at the time.

Set against the kami of the older tradition, which are attested across many centuries, shinigami is a late arrival. Anyone describing it as an ancient Japanese belief is off by well over a thousand years, and the figure took shape in an era of commercial theatre and printed popular fiction rather than in myth.

What anime did with it

Two franchises define the word for most English speakers, and they invent freely. One gives its death gods a bureaucracy, notebooks and a boredom problem. The other builds an entire afterlife civilisation with uniforms, ranks and a military academy, and its English release renamed them soul reapers rather than translating the term.

Neither is drawing on a fixed traditional figure, because there is no fixed traditional figure to draw on. The Edo material is thin and inconsistent, which left an unusual amount of room, and that room is why the two versions have almost nothing in common.

Why the ancient-myth version is so sticky

Partly the kanji. Characters look old, and a word written in them reads as inherited even when it is recent, which is a trick English cannot play on its own speakers.

Partly the Grim Reaper. English arrives already holding a robed personification of death and slots the Japanese word into that shape, and the fit feels natural enough that nobody checks the date.

The accurate version

A comparatively modern folklore figure, loosely defined, popularised on the Edo stage and in print, and then substantially reinvented by twentieth and twenty-first century fiction. That is a better story than the ancient one, because it is a case of a culture producing a new supernatural figure recently enough that the paper trail survives.