The first commercial item that was branded as such, was in Sept 82:
a Alpenlite pack, their "Superlight" model made out of their "Weatherlite" fabric and featuring their "Technolite" internal frame (They REALLY wanted to emphasize that it was "lite", LOL) The pack capacity was 2600 cu. in., weighted 24 oz. and cost $73 bucks (a princely sum back then). I still have it.
The motivation for coughing up the money for that purchase, was a result of my first homemade UL pack which I made & used just the month before. It was Fred Williams inspiration (from the July 82 Backpacker magazine) I made it for a late August Sierra trip which my buddies and I were competing on who would be carrying the lightest weight. The pack was approx 2200 cu. in., and weighted 20 oz. It lasted the whole week of the trip ... barely ... with a little duct tape help. My lack of sewing workmanship and my lack of knowledge on how to baby it, greatly contributed to its wear.
My standard pack before all that, was a frameless Jensen, which I shaved down (ala Doug Robinson) to 2 lbs. That pack was made from bomber cordura, no real babying required.
But alas, the allure of counting ounces had settled in, and I went on to lighter options.