The horizontally-split rear window is a design trope that, in 2017, is associated with hybrids - the Prius (except Gen 1), Insight, Gen 1 Volt, and Ioniq all have it, and the Gen 2 Volt evokes it. However, it’s certainly not exclusive to hybrids, and I felt like writing something about the non-hybrid applications.
Fundamentally, horizontally-split rear windows are a nod to practicality. Aerodynamically-optimized designs, especially in smaller vehicles, tend to have poor rear visibility, and the horizontally-split rear window allows a second pane of glass in a vertical portion of the body, below the normal rear window. That’s the reason for its usage on hybrids - they’re aerodynamically-optimized, and therefore need it - but it’s certainly not exclusive to them. Also, most of these (with the exception of the 8th and 9th-gen Civic Hatchbacks, which are more vertical hatchbacks, the Murano CrossCabriolet, which is a convertible, and the Alfa Romeo/Zagato TZ3s) are liftbacks of some form.
Its first appearance, as far as I’m aware, was on the 1967 Jaguar/Bertone Pirana concept, based on the E-type, and designed by Marcello Gandini, although the rear glass didn’t move with the hatch:
The very next year, another Gandini design - the Lamborghini Espada - included the styling trope, bringing it to production:
BvdV - The Dutch Engineer brought up the Maserati Khamsin, from calendar year 1974/model year 1975:
Bluecold reminded me of the Citroën SM breadvans, from the mid 1970s - seems Citroën rallied them, although I’m not sure of the provenance of this one:
TVR used a split rear window on the Tasmin (from 1980), per sdwarf36:
Honda continued the design with the second-gen Honda CRX for model year 1988, which incorporated it into the liftgate, and was the template for all modern implementations of the idea:
Mazda released their CRX competitor, the MX-3, in MY1992, and felt that the split window was a good idea, and put a tiny window underneath their spoiler, which counts:
Also thanks to BvdV, Mazda further embiggened that idea, for what was called the Familia Neo in Japan, the 323C in Europe, and the 323 Neo in Canada, for what we in the US would call model year 1995:
1999 saw further implementation of it on concept cars - Honda had the VV concept, which was a near-production-ready version of the Insight (and a spiritual successor to the CRX HF), which would go into production that year for model year 2000, but in the non-hybrid realm, Pontiac showed the Aztek concept:
That concept eventually came to production as the Aztek, for model year 2001:
And, the same year, Europe picked it back up, with the Mercedes-Benz C-Class SportCoupé (CL203), which we received as the C230 Kompressor:
Also from Bluecold, Citroën released the C4 with a split rear window in the 3-door models, in 2002:
The 8th-generation European-market Civic, circa what we in the US would call model year 2006, was a strange implementation - it had a more vertical rear window, but used unnecessarily split rear glass to implement its rear spoiler - probably a nod to the CRX, as well:
Thanks to dogisbadob, I completely forgot about the 2010 Honda Accord Crosstour having a split rear window:
They also reminded me of the related 2010 Acura ZDX having one:
Thanks to Rainbow, I’ve been informed that the 2011 Nissan Murano CrossCabriolet had a split rear window in its convertible top:
Bluecold also reminded me of the Alfa Romeo/Zagato TZ3s - the TZ3 Corsa (above) being a derivative of the 8C Competizione, the TZ3 Stradale (below) being a derivative of the Dodge Viper:
The Hyundai Veloster, from model year 2012, is an odd one, as it has a nearly flat roofline, but still has the split rear window thing going on - I’m suspecting an explicit attempt to evoke the CRX here:
The 9th-generation European Civic, from what we’d call model year 2012, continued the 8th-gen’s trend, but in a more pronounced manner:
Compared to previous European Civics, the 10th-generation Civic hatchback has more of a fastback profile, but still picks up that design trope of simulating one piece of glass split by the spoiler:
If I’ve forgotten any models, please post them up.
Edit: Added the Murano CrossCab.
Edit: Added the Maserati Khamsin, Mazda Familia Neo, Honda Accord Crosstour, Acura ZDX
Edit: Added the Citroën SM, the Citroën C4, and the Alfa Romeo/Zagato TC3
Edit: Added the TVR Tasmin