OK, Webster's doesn't help us much! But think about it--when family comes home, where do you all eventually end up? In the kitchen. The savory aroma draws you in and it's where you can really "be yourself" (dirty dishes and all!).
The key concepts for a kitchen environment are "family", "change", and "closed". When you're welcomed into the kitchen, you know you're family! When lives connect at the deepest, most real levels, change happens. But for this sort of life-on-life connection to occur, people have to feel secure...and that requires a predictable (closed) environment.