This is about stretch. It's the code name of the current stable Debian release, and it's also a tag on the main site.
Most of the usage seems to be about debian-stretch -- there are 19 questions tagged stretch, of which 10 are tagged debian stretch and 6 are tagged linux stretch, only one of the latter not also being tagged debian. However, there is at least one question thrown into the mix that appears to have to do with graphical artefacts rather than Debian.
I strongly suspect that most of the questions tagged stretch can be retagged debian-stretch with next to or no ill effects. That would also go in line with debian-lenny, debian-squeeze, debian-wheezy and debian-jessie.