Why do they call it kindergarten?

Reesing was hanging out at mom's work with her the other day and the below conversation took place between the two...

Reesing: Mom?

Mom: Yes Reesing?

Reesing: Do you know why they call it kindergarten? 

Mom: No, actually I don't. 

Reesing: Well, to my knowledge there are no flowers? There is no garden? It doesn't 'to make sense ?

Mom: What are you talking about?   Oh...yes, "kinder-garden." I can see how that is so confusing. You are very smart Reesing.

Reesing: I know .