A boilersuit or coverall is a loose fitting garment covering the whole body except for the head, hands and feet. The word boilersuit first on 28 October 1928 in the Sunday Express newspaper. The garment is also known as an overall in some places, but that word can also mean a bib-and-brace overall, which is a type of trousers with attached suspenders. A more tightfitting suit is usually called a jumpsuit.
The first mention of boilersuits known here is in a special rule for manufacturing explosives, laid down in 1891: "Overall suits and head covering shall be supplied to all workers…"
A boilersuit, or coverall (US English), is a one-piece garment with full-length sleeves and legs like a jumpsuit, but usually less tight-fitting. Its main feature is that it has no gap between jacket and trousers or between lapels, and no loose jacket tails. It often has a long thin pocket down the outside of the right thigh to hold long tools. It usually has a front fastening extending the whole length of the front of the body up to the throat, with no lapels. It may be fastened with buttons, a zipper, velcro, or snap fasteners. Boilersuits with an attached hood are available. The word "boilersuit" may also refer to disposable garments such as DuPont's Tyvek suits.
Boilersuits are so called because they were first worn by men maintaining coal-fired boilers. To check for steam leaks or to clean accumulated soot from inside the firebox of a steam locomotive, someone had to climb inside, through the firehole (where the coal is shovelled in). A one-piece suit avoids the potential problem of loosened soot entering the lower half of one's clothing through the gap in the middle. As the firehole opening is only just large enough for a fit individual to negotiate, a one-piece suit also avoids the problem of the waistband snagging on the firehole as one bends to wriggle through, or of jacket tails snagging if one has to come out backwards.
Usage of boiler suits 
Coveralls are most often worn as protective clothing over "street" clothes at work, but sometimes instead of ordinary jacket and trousers.
Similar coveralls made of Nomex in olive drab (and more recently, desert tan) are also used by the crews of armored fighting vehicles in the US Army and Marine Corps, where the men and also their overalls are sometimes called "CVCs", an abbreviation of "Combat Vehicle Crewman".
More form fitting coveralls with many zippered pockets, originally made of cotton treated for flame resistance, but made of Nomex since the late 1960s, have been used as flight suits since the beginning of WWII.
Coveralls called student overalls are used by university students in some Nordic countries as a sort of party-uniform, with insignia on the back and color varying with program and university.
For fans of the horror genre of film, the boiler suit is irrevocably associated with the slasher sub-genre, being regularly worn by both Michael Myers of the Halloween films and by Jason Voorhees of the Friday the 13th franchise.