Many authors attribute the term “junk science” to Peter Huber and his use of it in the term in his book, Galileo’s Revenge: Junk Science In The Courtroom (1991). As important as Huber’s book was to raising judicial consciousness to what was going on in courtrooms around the United States, the phrase “junk science” clearly predates Huber’s book.
Lawrence Hubert and Howard Wainer note that the phrase appears to have been in use by the early 1980’s, and sugggest that the first use of the pejorative phrase occurred in a Reagan administration white paper. Lawrence Hubert and Howard Wainer, A Statistical Guide for the Ethically Perplexed 460 (Boca Raton 2013). The document cited by Hubert and Wainer notes:
“Another way in which causation often is undermined – also an increasingly serious problem in toxic tort cases – is the reliance by judges and juries on non-credible scientific or medical testimony, studies or opinions. It has become all too common for “experts” or “studies” on the fringes of, or even well beyond the outer parameters of mainstream scientific or medical views, to be presented to juries as valid evidence from which conclusions may be drawn. The use of such invalid scientific evidence (commonly referred to as “junk science”) has resulted in findings of causation which simply cannot be justified or understood from the standpoint of the current state of credible scientific and medical knowledge. Most importantly, this development has led to a deep and growing cynicism about the ability of tort law to deal with difficult scientific and medical concepts in a principled and rational way.”
United States Dep’t of Justice, Tort Policy Working Group, Report of the Tort Policy Working Group on the causes, extent and policy implications of the current crisis in insurance availability and affordability at 35 (Report No. 027-000-01251-5) (Wash.DC 1986). So according to the Justice Department authors, “junk science” was already in common use by 1986. We really would not expect linguistic creativity in such a document.
Whence comes the phrase “junk science”? Clearly, the phrase is an analogue of “junk food,” food that fills but fails to nourish. Here is the Google ngram of the emergence of the phrase “junk food,” which shows the phrase took off in common use shortly before 1970: 
What then about junk science?
With a little tweaking of Google’s smoothing function, this search can be run to reveal more about the low end of the curve.
This chart suggests that there was very small flurry of usage in the first half of the 1970s, with a re-emergence around 1982 or so, and then a re-introduction in 1985, with a steady increase every since.
Here is how “junk science” compares to “junk food” (with more smoothing to the curve added):
Junk science seems to have overtaken junk food in books, at any rate.
Of course, “junk science” is an epithet to be hurled at science that the speaker dislikes. It has an emotive content, but its persistence reflects that it has an epistemic content as well. “Junk science” is science that lacks an epistemic warrant, and pretends to be something that it is not. Honest scientists, engaged in hypothesis-generating work, should not be defamed as junk scientists, but the boundary between hypothesis generation and conclusion mongering is often blurred by advocate scientists of all political persuasions.
There are many synonyms for junk science, which has been with us ever science gained prestige and persuasiveness over religious pronouncements about the real world. To avoid the politicization of the term “junk science,” here are some alternatives:
advertising
alternative medicine
alchemy
anti-vaccination movements
aroma therapy
astrology
baloney
blackguardism
blood letting
bogus science
bullshit
bunk
bunkum
cargo cult science
clinical ecology
cold fusion
creationism
cult
denialism
dodgy data
error
faith-based science
flim-flam
flotsam and jetsam
fraud
free-energy devices
fuzzy thinking
homeopathy
ignorance
intelligent design
junk science
Lysenkoism
magical thinking
magnetic therapy
miracles
misrepresentation
New Age science
nonsense on stilts
N rays
nostrums
not even wrong
paranormal phenomena
pathological science
phrenology
political science
propaganda
pseudoscience
pseudosymmetry
quackademic
parapsychology
quackery
rubbish
shamanism
spiritualism
voodoo science
