I was born and brought up in Drumchapel and can tell you that "Girnin" in Glasgow is a kind of whining sound that's not possible to explain without actually demonstrating the sound so you can hear it. The "girnin" in this instance refers to the sound the gates made when they opened and closed, much like any old rusting gates, so you can possibly imagine what that sounds like.
If you complained to your mum in a whining way about how someone wronged you, she would tell you to "Stop girnin!"
Glasgow City Council (in an amazing display of their infinite wisdom) tore the gates down (they claim) because of vandalism, but I was told (as a youngster) that it was because they couldn't be bothered maintaining them and (allegedly) had plans for the land on which the gates sat. The land sat empty for as long as I've known.
I hope this helps.