A kind of cutesy way of telling someone they're spending too much time grousing about something. Useful for children, spouses, and anyone else you'd really like to tell to STFU, but don't want to be really mean.
OK, Grumbellina, we get it, you don't like McDonald's, you can stop talking about it now.
A girl who is looks like she grew up under a rock and rarely saw sun-light. Ussually hunched and deformed in some minor way, but in dark settings can look somewhat slayable.
Guy- "Whooaa buddy that girl your wheeling is definately a Gremblin"
Dunsmore- "I know but as long as I keep her out of direct sunlight I will be able to slay her"