As featured in Waterline Summer 2025

The Words Behind the Water
Etymology in Legionella Risk Management

By Richard Danielson. MWMS (Snr). Second Element Ltd.

After watching Stephen Fry on an old episode of QI, explaining the surprising origins of familiar words… (did you know the word ‘freelance’ comes from medieval knights who were not aligned to a specific lord and hired themselves out for battle?) …I thought it might be interesting, or at least ‘Quite Interesting’, to take a look at some of the words we use in our own corner of the world.

Etymology! That’s the fancy name for the study of the origins of words and often reveals another layer of meaning. In the field of water hygiene, much of the language we use is technical, shaped by science and engineering. Terms like Legionella pneumophila, biofilm, and aerosol are part of the everyday vocabulary for those of us working to manage water systems safely, but a quick dive below the surface reveals that these words often have a story.

Hopefully, there’ll be a surprise or two to follow… or at the very least, a mildly curious “huh” with an accompanying raise of the eyebrows.

Legionella
The origin of the name Legionella is known to most of us in the industry. It came about following the 1976 outbreak at a convention in Philadelphia. The newly discovered bacterium was named after the affected group: the American Legion veterans.

It follows the convention in taxonomy (another fancy word that covers the branch of science concerned with classifying organisms) where the name of the genus often nods to an associated event, location, or person.

Other examples include Escherichia coli (E-coli) named after German paediatrician Theodor Escherich, who discovered it; and Salmonella, named after American veterinary pathologist Daniel Salmon.

The suffix -ella often refers to ‘a little’ or ‘smaller version of’ but is also a favourite of microbiologists who do love a little Latin flare.

What’s less widely known about legionella though, is that it could have been called something entirely different. A similar outbreak occurred three years earlier during a convention of the Independent Order of Odd Fellows (they sound fun at parties). It wasn’t investigated or linked at the time and only gained attention after the Legionella discovery. I can’t help wondering how different things might have sounded had the Odd Fellows case led the headlines and perhaps then we would be talking about Odd Fellow’s Fever rather than Legionnaires’ disease…

Pneumophila
Legionella pneumophila, is the species that has us all paying attention. While the genus Legionella points to the circumstances of discovery, the species name pneumophila gives us a clue as to the bacterium’s behaviour. The word comes from two Greek roots: pneuma, meaning “breath,” “air,” or more specifically, “lung,” and philos, meaning “loving” or “fond of.” Together, pneumophila literally means “lung-loving.” Quite an expressive name, accurate, and unsettlingly affectionate.

Bacteria
The word bacteria again has its origins in ancient Greek and comes from baktron, meaning “stick” or “staff.” The term was coined in 1838 by German Christian Gottfried Ehrenberg, who used it to describe the stick-shaped organisms he was seeing under his microscope.

Aerosol
Aerosol is a word that wears its science lightly. Despite its technical origins, it has crossed into everyday vocabulary with ease, on one occasion while delivering Legionella awareness training, I was asked if there’s a Legionella risk from Lynx Africa … for the uninitiated, that’s deodorant … and erm…well no, different kind of aerosol.

In water hygiene though, aerosols are a critical concept, and the route of transmitting Legionella bacteria deep into the lungs to cause infection.

The word Aerosol itself is a relatively modern invention 1920-ish, but is built from classical roots: aero, from the Greek aēr (air), and sol, short for solution, from Latin solutio. So, in essence, an aerosol is a “solution in air”, that misty mix of particles in a gas that we are so cautious of.

Biofilm
“A nature documentary?” said my Lynx Africa friend when I ask him later if he knew what a Biofilm was… erm, again… no… (honestly – LCA auditors these days – I’m kidding! (sort of) no really, I’m kidding …please don’t blacklist me) Etymologically at least, it’s almost poetic: bio from the Greek bios, meaning “life,” and film from Old English filmen, meaning “a thin layer” – literally a layer of life. Not a bad name at all for a stubborn, slimy matrix of microbes …ah, now there’s a word…

Microbe
Microbe was coined in 1878 by the French military surgeon and biologist Charles-Emmanuel Sédillott in a lecture to the French Academy of Medicine, he proposed it as an alternative to the terms in use at the time – animalcule (although I quite like that!). Built from the Greek mikros (small) and bios (life), microbe referred to all ‘small life’, and so the word caught on and was quickly adopted.

Calorififier
Of all the terms in the water hygiene world, calorifier is possibly my favourite. It has the ring of something you might find in the engine room of a Jules Verne novel, right next to the transmogifier and tended by a man in a waistcoat with leather gloves and tinted goggles! The word comes from Latin: calor meaning “heat”, and the suffix -ifier, from facere “to make or do”. So, quite literally, a calorifier is a “heat-maker.” It’s a beautifully old-fashioned word that persists mainly in our industry, and one that I catch myself automatically explaining to clients: “We’ve tested your calorifier… you know … the hot water cylinder.” Hard to argue with the efficiency of calorifier.

Sentinel
Sentinel is one of those words that feels quietly reassuring. In our water hygiene world today, a sentinel outlet is one we select for routine temperature checks to represent the broader system, but the word itself comes with a far older lineage. Its roots lie in the Latin sentire, meaning “to feel” or “to perceive.” Through Old Italian (sentinella) and French (sentinelle) and evolved into its current English form to mean a watchful guard or lookout.

Hygiene
Hygiene has a clinical neatness to it, but its roots are surprisingly mythological. It traces back to Hygieia, the Greek goddess of health, cleanliness, and sanitation. The daughter of Asclepius, god of medicine, Hygieia’s role was preventative: not healing illness, but maintaining health and warding off disease before it had a chance to take hold. The word made its way into English via Latin (hygiena) and over time, hygiene became our word for practices that preserve health through cleanliness and prevention. So, in the words of Stephen Fry, “we leave you now with this…” For those of us in water hygiene, it’s a rather elegant reminder: success is often found not in what we fix, but in what we prevent.