A curious thing has happened to pipeline. The word—although originally, as happens with many words, as two separate words—is first recorded by the OED in the early days of the oil industry in the last quarter of the 19th century. Its first metaphorical use was recorded in Aldous Huxley’s first novel Crome Yellow (1921). Not long after that it became hyphenated, and then one word in the late 1940s. Turning nouns into verbs is nothing new: pipe-lining—in the literal sense of moving oil—appeared in the Pall Mall Gazette in 1886. The OED also records the adjective pipelined, the noun pipeliner, and the verbal noun pipelining.

Pipeline first appeared in PubMed in 1974. Most of the early occurrences are literal. There is the occasional metaphor—a pipeline of communication, the medical graduate pipeline. In 1978, the “bogus pipeline” procedure appears in PubMed, a psychological technique to reduce false answers when collecting self-reported data, but that only accounts for a few articles, about 40 in all. By 2000, there are 42 pipelines, many still literal, or simply a channel for moving something other than oil, but there are also a few of the abstract metaphor “in the pipeline”, whose first appearance was 1991.

But not long into the new millennium, the curious thing happened. In 2000, about 0.01% of all articles in PubMed published in English had pipeline in the title or abstract. By 2005 it was 0.05% and it has gone on increasing such that in 2015 it was 0.16%: a 14-fold increase since 2000. This is a phenomenal increase. Table 4.2 in our medical style book lists searched words whose prevalence has increased between 1975 and 2010. Ignoring gender (which had increased 44-fold, but for which there are obvious explanators), the top four were address, addresses or addressed; option or options; strategy or strategies; and the adjective novel. But even these front runners, all of which have increased about two-fold between 2000 and 2015, lag well behind pipeline.

Note that I wrote “searched words”: one can only search for words one thinks of (although there will be algorithms that can search on all words). We didn’t think of pipeline. What is going on? There has been no change in the occurrence of pipeline in general English (see Ngram).

Searching websites for synonyms does not give any words other than literal ones for pipeline. But scanning recent PubMed searches for pipeline, the word seems to be used to mean system or scheme: “…a comprehensive pipeline using a combination of… software”; “There is a need for pipelines that unify data mining and inference deduction…” The word seems particularly popular in the fields of gene-mapping and others that need complex analysis by computer. And sure enough, that is what it is: a chain of processing elements in software engineering.

But that’s not all: there is also “a robust pipeline of investigators from the communities…”. And that is a metaphor too far.

Neville Goodman is a retired consultant anaesthetist and a writer. He is co-author of a book on medical English.

Competing interests: I have read and understood BMJ policy on declaration of interests and declare that my only competing interest is my co-authorship of a book about medical English.