It was originally invented after WW1 by a guy called Arthur Scherbius, who got a patent on the way the machine worked and started a company with E. Richard Ritter called Scherbius & Ritter. They attempted to sell the machine to the German Navy & Foreign office, but at that time they were not interested.

At some point they got involved with another company called Gewerkschaft Securitas and between them formed Chiffriermaschinen Aktien-Gesellschaft.

They concentrated on commercial sales, these pre-war versions were used by various organisations in several countries.

From there, as war loomed and the Germans started building up their forces military versions of the enigma started to appear.

I found a whle bunch of documents on the history here: http://cryptocellar.org/enigma/

And an extract from a book here : http://www.apprendre-en-ligne.net/crypto/bibliotheque/PDF/KruhDeavours.pdf