R. E. Howard's Worms of the Earth was published in 1932. C. L. Moore's Black God's Kiss was published in 1934. She was 23. He was 26.
Both were stories written by young writers and, in the case of Moore (or that's my understanding,) her story seems to be part of her young or apprentice phase (in my opinion, Howard was already old when he was born.) Why am I mentioning all of this? Well, because I think the Black God's Kiss would not have existed without the Worms of the Earth. In fact, one could argue Moore's story is a retelling of Howard's short story. Writers of that Weird Pulp era were part of a small circle, so these of influences and borrowings were standard and, sometimes, encouraged. For example, the Worms of the Earth borrows heavily from H. P. Lovecraft Cthulhu Mythos.
Both stories begin with the protagonist, the ruler of a nation, witnessing an evil against their people at the hands of invaders (actual or potential.) In Black God's Kiss, Jirel of Joiry is captured and humiliated by Guillaume, who also captured her castle and, it is assumed, her lands. In R. E. Howard's story, the Pictish king, Bran Mak Morn, is forced to watch the crucifixion of a fellow Pict, an execution ordered by the cruel Roman governor Titus Sulla.
In both stories, the protagonists swear revenge against a villain that is beyond their grasp. To accomplish their impossible goals, they need a demonic or monstrous tool. The tribal king wants the help of "The Worms," ancient Lovecraftian creatures one of his ancestors had banished a long time ago from the surface of the Earth. Jirel goes down to an almost literal Hell to seek something she suspects it is there and that will help her get her revenge. And in both cases, the protagonists are told that they are playing with dark forces and that no mortal enemy deserves to die at the hands of Them (or It.) Again, both of them descend to a Hell-like landscape to get the help/tool they need. Morn needs to steal the Worm's Black Idol, which will allow him to blackmail the creatures and force them to kidnap Titus Sulla in exchange for the idol. Jirel, on the other hand, "steals" a kiss from a Black Idol.
The descent to Hell is, in both stories, so similar I can imagine C. L. Moore reading that story and, during that scene, realizing she had to write a story like that one. In both stories, the protagonist descends through serpentine and claustrophobic (a feeling masterfully evoked in Howard's story) tunnels, passages that were clearly not made for humans. Both places speak of an ancient and alien evil, and both lead to a hell-like domain. Whereas in Howard's version, it is a purely terrestrial place (although psychologically speaking it is not,) Moore uses that descend to create a Dantesque extraterrestrial landscape where half the story occurs.
Once the protagonists got what they wanted, they return to the surface, only to realize they made a pact with a devil. Morn discovers the destruction the Worms have caused, and when they give him what he wanted (the Roman governor, his mind now completely broken,) he understands that not even a Roman deserves that fate. At the same time, Jirel realizes too late the true nature of her feelings for Guillaume, but to save herself she has to kiss him, an action that destroys the body and mind of Guillaume, not unlike what happened to Titus Sulla.
Comparing Moore's story to Howard's may be a bit unfair. Worms of the Earth may easily be one of his best tales, and it has a strength and power that you almost never see even in the sword & sorcery genre. Still, I simply could not have passed over their similarities. And differences.
Even if I did not know that the C. in C. L. Moore means Catherine, I think I would have deduced the author was a woman after reading The Black God's Kiss. I am not saying it in a negative way, by the way, but this is clearly a woman's story. The probability that any men would have written this story, although not 0, is nonetheless small. In fact, at least in our contemporary cultural and critical landscapes, if any man had tried to write this, he'd probably had suffered the wrath of the Cultural Police.
That is, by the way, what true diversity means; it means tales written by different minds, not the same characters and plots under differently colored or gendered garments. It is not the quota-driven attempts at representation, mandated by studies of current demographic targets, where skin, genders, and identities can be swapped like someone swaps dresses, but the deep-seated, mostly invisible and hidden drives that distinguish the fantasies of a man from those of a woman (or those between people with widely different personalities, for that matter.) You simply cannot change the sex of Jirel and Guillaume and assume the story is still the same or that it still would make sense.
But if this had happened recently, if an author had written a fantasy classic and someone had tried to do a gender-bending version of it, that is exactly what would have happened. The barbarian warrior would have been changed for a barbarian princess, but her psyche, motivations, fears, and desires would still be masculine. Or worse, Jirel of Joiry would become Jirolio of Joiry, and then we'd have to try not to laugh ourselves to death at the thought of that powerful warrior giving the kiss of death to the conquering amazon he loves but hates at the same time because she had tried to humiliate him with a forced kiss.