Eneloop. It's a thing, not a typo.

As I glanced at my new pack of batteries, I though the thing had a typo on the package. I mean, what do envelops have to do with batteries? And considering the things are by Sanyo - a rather well known brand - that'd be rather embarrassing. Eneloop is Sanyo's brand of rechargeable batteries that supposedly last a good long time between charges.

You can find find eneloop batteries in many places.