Humans have presumably made use of safety reserves
since the origin of our species. They have added extra
strength to their houses, tools and other constructions in
order to be on the safe side. However, the use of numerical
factors for dimensioning safety reserves seems to be of
relatively recent origin, probably the latter half of the 19th
century. The earliest usage of the term recorded in the
Oxford English Dictionary is from W.J.M. Rankine’s book
A manual of applied mechanics from 1858. In the 1860s, the
German railroad engineer A. Wohler recommended a
factor of 2 for tension [31]. The use of safety factors has
been well established for a long time in structural
mechanics and its many applications in different engineeing disciplines. Elaborate systems of safety factors have
been developed, and specified in norms and standards