I said "WTF I've never heard of osiris having daggers"
Neither did I
And neither did I find anything really relevant on google. What follows is as such wondrously pointless.
I remember he was usually depicted with the scepter and the flagellum... and I vaguely remember Seth did cut his corpse in several pieces, but no mention of daggers that I know of (well, it's been at least 10 years since the last time I read anything about ancient Egypt myths, so I might well be wrong).
I'd say it could be from some work of fiction (or art... just like Luis Royo has mixed and matched asian myths for a couple of his artbooks) loosely based on a certain symbolism: Osiris' spine was usually symbolized by the Djed (needless to say, I wikied it for the name
), a pillar, and in some depictions this gets mixed with his curvy scepter and a snake.
So, we have a sort of "rippled" spine, kind of consisting with the symbolism the bigger dagger would have had, Osiris was a god of the afterlife so it comes natural to think of sacrificial daggers (not that they used the kriss or keris in Egypt, that's more of an Indian shape, but still...), plus pretty much everyone has plundered these gods for everything, from science fiction to D&D settings, so it's all become pretty confused. There might be this vaguely related imagery (or it might be me trying really hard
), but the whole thing about these daggers being made for the kings a-la LotR (if that is indeed the case) smells fishy: there almost always was one and only one pharaoh at any one time. Not so much semantically as he was a God-King (there were quite some differences between dynasties on that matter), but simply because Egypt was pretty much unified since 3000 BC and there never were different pharaohs at odds except for a couple of short periods; it doesn't seem a very likely scenario for such a legend to come up unless a modern novelist went a bit fantasy on it (Christian Jacq I'm pointing mah finger at you).
Also, then there are those tattooers who suggest you subjects they dreamt of the last time they were so stoned they'd swear it was Osiris himself who told them the story, so... who knows, hopefully the premise will click with someone else's memory.
tl;dr;
Sorry I couldn't be of help, I wasn't able to think inside the chimney
