Install, or installation, is a very common word to society. We see it all the time, especially when using computers and software. However the definition of install was very different several centuries ago. The Oxford English Dictionary officially defines install as “To invest with an office or dignity by seating in a stall or official seat, as the choir-stall of a canon in a cathedral, or that of a Knight of the Garter or Bath in the chapel of his order, the throne of a bishop, etc. Hence, to instate in an office, rank, etc. with the customary ceremonies or formalities. Often with object or adverbial complement.” (OED). Traces of this definition can be seen as early as the mid 1500s in terms of appointing religious figures such as cardinals and bishops. Install does not have a Proto-Indo-European root, but it does find a root in Medieval Latin and Old High German. Such roots include Stall and Installa. The root to stall is similar to install in that stall is defined as “Standing-place, place, position; place in a series, degree of rank; in Old English occas. state, condition.” (OED).
While the installation of bishops, and other members of society holding offices of dignity, is still an occurrence in society the more common use of install finds its roots in the French installer. The French installer finds its earliest use in the mid twelfth century as describing “one who installs” (OED). This reference and subsequent definition of install are closer representations of how we use the word today. When someone speaks about installing, they are referring to installing software on a computer or installing machinery. The Oxford English Dictionary has a definition for this use and it speaks about placing an apparatus in position for service or use.
"install, v.1". OED Online. September 2012. Oxford University Press. http://www.oed.com/view/Entry/97023 (accessed November 21, 2012).