You made me curious and some quick duckduckgo-ing led me to a biologists involved-if-not-comprehensive investigation of the origins of the term [0]. Long story

You made me curious and some quick duckduckgo-ing led me to a biologists involved-if-not-comprehensive investigation of the origins of the term [0]. Long story short, it probably dates to late 1950s Cambridge and may have originated with Francis Crick, co-discoverer of the structure of DNA. Of relevance is that it preceded the discovery of mRNA, dating to a time when all RNA was thought to be ribosomal DNA. At that time the prevailing theory was that DNA codes for RNA that is incorporated into the ribosome (which then makes proteins). Because the amount of RNA code in the ribosome was clearly much less than the amount of DNA code in the genome, the implication was that much of the genome did not code anything, simply as a matter of mathematical difference. The term was controversial early on, and it might even have been coined to be so, though that's less clear. [0] https://judgestarling.tumblr.com/post/667709690372849664/the-origin-of-the-term-junk-dna-a-scientific https://judgestarling.tumblr.com/post/667709690372849664/the...