Down in the forest

Does anyone know the name of this plant in English? In Finnish it's called ketunleipä and an other name is käenkaali. Those mean fox's bread and cockoo's cabbage x D Hilarious. When I was little I used to eat them sometimes. They taste good and are not poisonous or anything. But you can't eat a lot of them at one time, because they have some acid in them, I don't remember what acid that was.. Maybe the same that is found in rhubarbs?

Edit: It's Common wood sorrel ^__^