I doubt it. Nearly all of the clothes we wear today are English in origin. Of course, it's also possible that the English simply stole the idea and refused to give credit. Possible, but I doubt it.
The word "English" is an evolution of Angles. The "original" British people were slaughtered wholesale by various invading primarily Anglo and Saxon (separate) tribes during invasions between 300-900 AD (the Angles, Saxons and VIkings all invaded in separate periods). Extremely few modern Londoners could claim indigenous bloodlines or cultural history. At some point, their blood is of Germanic/French/Viking (Danish) ancestry. Brian Boru claimed to be of an original indigenous (and non-gaelic, or true Celtic) bloodline of the "British Isles", hence his hatred towards (and victorious battles over) the "invading" Vikings in Ireland. What is interesting is that the name "Briton" came from Roman invaders, as did "Scots" to describe the war tribes of Ireland. Heh heh. The Celtics are the true indigenous peoples of the British Isles, along with the Pictish people, although they were considered Celtics by the other Celtics, and only the ROmans called them "Picts." As invading Vikings, Saxons and Angles variously slaughtered the indigenous Celtic people, they fled North to "Scotland." Kenneth MacAlpin united the Scots and Picts (reminding them they were all of Celtic blood) and defended the true indigenous (or Celtic) people from the repeated, continued raids of the Vikings and Saxons (and also began the process of a United Scotland). I guess my point is to say that everything English actually finds its origins in the Germanic traditions of the Angles and Saxons, including the language and the name itself, which would explain pants. Unless, of course, you are describing a Celtic custom. So to all you English people - you are not truly English unless you are Celtic. Heh heh. And you wear pants because that was the custom of the barbarians who invaded and settled England. Pants were the custom of Germanic barbarian tribes (the sight of which horrified quite a few Roman historians, as they left quite colorful descriptions of their first encounters with pants). Anyways... that's my little tidbit about pants. But I wasn't sure where the distinction lies between pants and trousers, and how the name "trouser" came about, although Manton's previous post may have explained it.