Merriam-Webster tells us the leisure suit fully arrived in 1975, and that may be [source: Merriam-Webster]. But that's the "leisure suit" of the 1970s. The introduction of a lightweight, comfortable pants-and-jacket set intended for casual occasions, or no occasion at all, came well before the disco era.
The origins of any particular fashion can be tough to pinpoint, elements often evolving over years, even decades. A "lounge suit" pops up as early as the mid-1800s in Britain, basically a less-structured daytime suit with the jacket and pants made in non-matching fabrics.
The more modern idea of the leisure suit dates back at least to the 1920s, when a sort of post-World War I relaxation was taking hold in the United States [source: Goldstein]. The roaring '20s brought the usual youth rebellion seen in any era, showing up, as it often does, in the clothes -- women in boyish "flapper" attire and men in loose-fitting suits that looked sort of like tailored sacks. In fact, they're sometimes called "sack suits." These leisure suits were a significant departure from the older generation's long coats, vests and snazzy, striped trousers.
None of these early leisure suits incorporated polyester, of course, since it wasn't invented yet. That happened in the 1940s in the U.K. By the following decade, polyester had gained some popularity in the United States, and in 1970, the leisure suit -- or more accurately, the Lee-sure suit, manufactured by Lee Jeans -- made it's very first appearance [source: Fashion Encyclopedia]. Taking its cue from such styles as Yves Saint Laurent's "safari suit," the Lee-sure suit aimed for a laidback look with style.
Whether the suit achieved that goal is up for debate (or not). But no one denies the leisure suit's impact. It has come to signify the disco side of the '70s…