Foul-Mouthed Rebellion

French Snack's stories feature a character named Amrine, a harpy who came to the Felaryan mainland from Iracal Island, a settlement so isolated that Amrine is practically an off-worlder. Amrine notably lacks the... colorful language of native harpies, as so many who meet her are quick to point out. This suggests that Harpies' foul language is not a hard-wired racial trait but a cultural quirk that is likely unique to the local harpies. What event could have happened in the history of the local harpies to spur this development?

The local harpies have the unique distinction of having been around Ur-Sagol when it was devising the translation spell. Perhaps, the Harpies and the Sagolians did not get along well at all. While other races were slowly accepting Sagolian rule more and more, and learning the Sagolian language to facilitate this, the Harpies refused to cooperate and stuck to their own Harpy language, excluding the Sagolians as much as they could. Then the translation spell hit, and suddenly the language barrier that the Harpies were exploiting dissolved overnight. The Harpies were not happy with this, and tried everything they could to break or circumvent the spell. Over time, they did in fact find a weakness: idioms and metaphors did not run through the translator very well, being translated in a literal fashion that often sounded confusing to the recipient. Over time, the Harpies adapted their language to exploit this for all it was worth, making their language so heavy with idioms, slang, and figurative speech that it became almost incomprehensible to anyone that wasn't "in" on it; this was the closest they could get to speaking a different language again. And then to top it all off, they made it vulgar as all get out, under the idea that those stupid Sagolians who tried to cheat their way into harpy language deserved to be insulted at every turn!