Language Change

when I logged out of Minecraft and logged back in later it wasn't in English. It happened while using creative one's medieval texture pack converted to a resource pack. Whenever I tried to change the language back and clicked the English button it would go back to a language I don't know. Pirate-Speak worked but I cannot understand it either. I tried it again under a different directory and it still happened. Then, I tried it under another directory without the pack and it didn't happen.