Note: In Britain, bell bottoms only refers to the sailors' trousers. In the 1960s they were known as flares or loons.
Bell-bottoms' precise origins are uncertain. In the early nineteenth century, very wide pants ending in a bell began to be worn in the U.S. Navy. Clothing varied between ships, however, since in the early days of the U.S. In one of the first recorded descriptions of sailors' uniforms, Commodore Stephen Decatur wrote in 1813 that the men on the frigates United States and Macedonia were wearing "glazed canvas hats with stiff brims, decked with streamers of ribbon, blue jackets buttoned loosely over waistcoats and blue ters with bell bottoms." Though the British Royal Navy usually was the leader in nautical fashion, bell-bottoms did not become regulation wear for the Royal Navy until the mid-1800s. These "bell-bottoms" were often just very wide-legged trousers, unlike modern versions cut with a distinct bell. While many reasons to explain sailors' wearing of this style have been cited over the years, most theories have little credibility because reliable documentation is lacking. In the 1960s, at least, U.S. naval recruits were taught to use their bellbottoms as life preservers by slipping them off, then tying the legs open and capturing air in them.
Bell-bottoms became very fashionable in the late 1960s and much of the 1970s, both for men and women. They began as part of the hippie counterculture movement in the 1960s, together with love beads, granny glasses, and tie-dye shirts; in the 1970s, they moved into the mainstream. Sonny and Cher helped popularize bell-bottoms by wearing them on their popular television show. They can, however, be seen as early as 1964,in the concert film, The T.A.M.I. Show worn by a young Toni Basil, who at the time was a go-go dancer in the film, and wore white "flares" with a baby-doll top.
Today, the original men's bell bottom pants and flares from the 1970s are collectible vintage clothing items. Worn by men to attend retro theme disco parties, worn in retro revival bands, and to wear clubbing - [mens bell bottom pants] are the most wanted of fashion items from the 1970s.
Loon pants (shortened from "balloon pants") were one type of bell-bottomed trousers. They flared more from the knee than typical bell-bottoms, in which more of the entire leg was flared. They were a 1970's fashion, and could initially only be bought via catalog from a company in Britain which advertised in the back of the New Musical Express. They were usually worn with a Led Zeppelin T-shirt and Jesus boots (sandals). They became associated with disco music. When the disco backlash started in 1979, bell bottoms started to go out of fashion along with leisure suits and other clothes that had become associated with disco.
In the mid 1990s a disco revival occurred and bell bottoms became popular again in women's and men's fashion in Europe spreading to the Americas. They were initially reintroduced as boot-cut (also spelled "boot cut" or "bootcut"), tapering to the knee and loosening around the ankle to accommodate a boot. Over time, the width of the hem grew wider and the term "flare-leg" was favored in marketing over the term "bell-bottom". As with boot-cut hems, the trend began in Europe and spread rapidly around the world. Today both boot-cut and flare-leg pants remain popular both in denim and higher quality office wear. In menswear straight-leg also gave way to boot-cut looks, again initially in Europe, and has made its leap into flare-leg for officewear, the same as what has happened in womenswear. In most cases men's boot-cut and women's boot-cuts differ. Women's jeans are tight to the knee and then flare out slightly to the hem while men's styles are usually flared/loose all the way from crotch to hem. The bell-bottoms of the 60s and 70s can be generally be distinguished from the flare or boot-cut pants of the 90s by the tightness of the knee.