Reliable Academic Source for the Etymology of "Trauma"?
There is an extra-detail in the article Psychotraumatology in Greece from the European Journal of Psychotraumatology that says:
The word trauma comes from the Greek trauma (τραύμα) meaning trauma wound, alteration of trōma; akin to Greek titrōskein = to wound, tetrainein = to pierce.
Then you might want to look for Caruth, Cathy, Unclaimed Experience. It speaks about the term being first used as a physical wound but then, with Freud, it begins to be used in psychology:
In Unclaimed Experience: Trauma, Narrative, and History, Cathy Caruth discusses the origin of the word "trauma," and the way Freud's analysis of it has shaped our modern understanding of the word:
...the Greek trauma, or 'wound,' originally referred to an injury inflicted on a body. In its later usage, particularly in the medical and psychiatric literature, and most centrally in Freud's text, the term trauma is understood as a wound inflicted not upon the body but upon the mind. But what seems to be suggested by Freud in Beyond the pleasure Principle is that the wound of the mind—the breach in the mind's experience of time, self, and the world—is not, like the wound of the body, a simple and healable event, but rather an event that...is experienced too soon, too unexpect edly, to be fully-known and is therefore not available to consciousness until it imposes itself again, repeatedly, in the nightmares and repetitive actions of the survivor. (3-4)
I am not sure you will find a detailed historic evolution of this word, but encyclopedias would be a good place to start.
This thesis also looks promising on at least providing titles of studies that speak about the origin and evolution of use of this word.