1926, apparently coined by South African Gen. J.C. Smuts (1870-1950) in his book "Holism and Evolution" which treats of evolution as a process of unification of separate parts; from Greek holos "whole" (from PIE root *sol- "whole, well-kept") + -ism.
This character of "wholeness" meets us everywhere and points to something fundamental in the universe. Holism (from [holos] = whole) is the term here coined for this fundamental factor operative towards the creation of wholes in the universe. [Smuts, "Holism and Evolution," p.86]
holism holds that the whole is greater than the sum of its parts
holey
holiday
holier-than-thou
holily
holiness
holism
holistic
holla
Holland
hollandaise
Hollander