way back
n.—Gloss: the backmost area of a station wagon (British: estate car), usually used for portage or storage. «I dare say that most people who are parents now never rode in a car seat as children. Many of us didn’t even use the car seat belts when riding around town. We scrambled to ride in the “way back” of the family station wagon.» —“Milk has an Expiration Date and so Does Your Car Seat!” by mmcphee Epinions Aug. 31, 2006. (source: Double-Tongued Dictionary)
Further reading
The cardboard cylinder left after the last sheet of toilet, tissue, or wrapping paper comes off the roll has inspired families to make up a lot of names for the tube or the sounds you can make with it. These include oh-ah, oh-ah, drit-drit, dah-dah...
There are lots of colloquial phrases to explain away the cacophony of a thunderstorm: The potato wagons are rolling, The tater wagon’s going over the bridge, The potato wagon broke down, and God is dumping out potatoes and washing them off. In...
This term has been in use for at least 40 years — since the ’60s heyday of the station wagon. Not sure I’ve even seen it written before, though.
Yeah, that’s why I included it here. It’s not any any of the dozens of dictionaries I checked.
As the youngest child in a large family growing up in suburban San Diego in the 1970s, I was often stuck in the “way back” of mom’s station wagon. It was not a place of honor.
This explains everything. My father-in-law used this phrase while greeting one of my kids as we picked him up from the airport. My daughter was seated in the last bench of our 12-seater van and he exclaimed, “Hey, way back Audrey! How are you doing?” We use the phrase now to address whomever is sitting in the back bench.