The funny(ironic) thing is. tabs as a desktop metaphor belong to the window manager.. however tabs, as implemented, were a revolt against window manager tabs.
If I understand history correctly, with the meteoric rise in popularity of our modern day terminal(the web browser) people were wanting to run more and more browsers at the same time. as the existing desktop manager state of the art(probably windows 95) was coming up short when dealing with the number of windows people wanted open the browser manufacture Netscape said fine, we will do it our self, this is where my memory gets fuzzy, I forget if it was an early firefox(phoenix anyone) the full mozilla browser or netscape proper(6 ish timeframe) that invented tabs, but they were and still are a very popular way control your many many browser windows you had open.
Really in the wrong layer however, it should be your desktop manager that provides tabs, not the application, and some do, but it is not a common thing what with the way DM tabs fight application tabs.
I remember when Phoenix got tabs, it was a killer feature for me because I was using some environment which didn't handle tabs itself (KDE and Windows). It was great not having to deal with a ridiculous amount of window buttons in the task bar.
But now, we've come full circle. I'm using i3 and adore its tabbed windows feature. However, it's basically impossible to disable tabs in current browsers. Firefox has some extensions [0], which combined with some custom css to hide the tab bar kinda sorta work if you're ok with a janky experience. For Chrome, I haven't found anything.
I am not sure that it was first, but Opera was the first browser that I remember having tabs. Outside of browsers, I think UltraEdit was the first application that I remember having tabs.
