Used in medicine, mathematics, and general writing in various senses including "growth to maturity and development of an individual living thing" (1660s). Modern use in biology, of species, first attested 1832 in works of Scottish geologist Charles Lyell. Charles Darwin used the word in print once only, in the closing paragraph of "The Origin of Species" (1859), and preferred descent with modification, in part because evolution already had been used in the discarded 18c. homunculus theory of embryological development (first proposed under this name by Bonnet, 1762) and in part because it carried a sense of "progress" not present in Darwin's idea. But Victorian belief in progress prevailed (and the advantages of brevity), and Herbert Spencer and other biologists after Darwin popularized evolution.
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]