Historically, it's a psychiatrist term (but these were the days when psychiatrists practiced more like how psychologists practice now, primarily doing psychotherapy). Here's some more info.
Courtesy of DearShrink.com:
What About the Word "Shrink"?
Originally, the word "shrink" referred primarily to psychiatrists, but over the last 20 years its meaning has broadened and now it can be used with respect to just about any professional who does counseling or psychotherapy.
"Shrink" likely originated from a commingling of the two words "head shrink" and the single word "headshrinker," indicating that it likely originated as a disparaging reference comparing the process of psychotherapy to primitive tribal practices of shrinking the heads of enemies. Reportedly, "shrink" was first used in literature by Thomas Pynchon in his book The Crying of Lot 49 published in 1966. It figures that "shrink" had its literary birth out of the consciousness-expanding atmosphere of the 1960s.
"Shrink" has paradoxical meanings and uses and, by all analytical standards, has classic potential for connoting ambivalence (a favorite shrink word!). "Shrink" allows us to compare psychotherapy to primitive rituals, shamanism, and "sorcery" while still recognizing the more modern and scientific principles of mental wellness. "Shrink" attempts to create a balance between respect and irreverence, between affection and distancing -- can't live with 'em, can't live without 'em.
To me, that is the essence of a good word -- one that has many flavors. What sweet and sour are for taste buds, paradoxes are for the mind.
I invite you to think of "shrink" as an appropriate, minor term of endearment -- a way of saying "psychiatrist" without creating that feeling that you are just being examined and not appreciated. After all, "psychiatrist" is not only a "big" word, but also a word that has potential for connoting a profession, which is mostly scientific and not very related to the humanities. As much as we psychiatrists would like to believe that psychiatry is mostly a science, by definition, since psychiatry deals with the mind at least as much as the brain, it has very little hope of being as scientific as, let's say, microbiology.
Wait, There's More!
The term "shrink" really does have its fair share of different belief systems. A posted e-mail follow-up at
www.psychiatry.com (no longer available) suggested that the term simply refers to the idea that psychiatrists have the ability to reduce or "shrink" one's mind into an understandable concept. Therefore, they are shrinks.
