In the early 1840s Samuel Ajayi Crowther published the first substantial Yoruba vocabulary. Crowther was himself Yoruba, taken as a boy in the slave trade, freed by a British naval patrol, educated in Sierra Leone, and later the first African Anglican bishop. In compiling his lexicon he needed a Yoruba word for the Christian devil, and he used Eshu. The choice was made by a man with real authority in both languages, and it stuck.
It stuck so firmly that Yoruba Bibles render Satan as Eshu to this day, that generations of Yoruba Christians grew up with the name meaning nothing else, and that popular writing in English about the orishas still describes him as a devil figure. The equation is now the single most common error made about the Yoruba pantheon.
What makes it an error is not that Eshu is gentle. He is not. He is dangerous when neglected, he tests people, he provokes, and his verses are full of ruin visited on those who withhold what they owe. What he is not is an adversary of the supreme being. There is no cosmic revolt in Yoruba theology, no fall, no realm of punishment ruled by an enemy. Eshu carries out Olodumare's arrangements rather than opposing them; he is closer to a customs officer than to a rebel. Reading him as Satan imports an entire cosmology of two opposed powers that Yoruba religion does not have, and once imported it distorts everything else, since a pantheon whose messenger is the devil must be a demonic pantheon.
The correction has been made repeatedly, by Yoruba scholars, by priests in Nigeria and in the diaspora, and in organised public campaigns. It is a useful case for anyone reading comparative religion, because the mistranslation was not imposed by a hostile outsider. It was made in good faith by a native speaker working inside a missionary project, and it shows how a single lexical decision can carry a foreign theology into a tradition and stay there for two centuries.