There’s something about this word that makes me think a bit of a stuffed-up nose – probably the taste of plug (in spelling but not in pronunciation) and the way phl makes me think of someone blowing their nose. But it has nothing to do with catarrh.
On the other hand, like catarrh, it also has a strong flavour for me of the scientific fancies of a bygone age, and the ph aids that too. I could picture some Chitty Chitty Bang Bang refugee called Phineas Pharnsworthy’s Marbhellous Phlogiston Steam Machine, all gears and flogging pistons and puffs of smoke, a combination jalopy and calliope.
Mind you, Chitty Chitty Bang Bang was set in 1910, putting it a century and a half after the heyday of phlogiston. But from our perspective, there’s something of a quaintness to those Victorian (and just-post-Victorian) inventions, and there’s a sort of quaintness to phlogiston.
But it seemed quite reasonable to 18th-century scientists. Here’s the idea: all flammable substances contain an element called phlogiston (from Greek for “burning up”) which is liberated during combustion. When wood is burnt, for instance, the flame is that part of it that is phlogiston – and it is liberated into the air – and the charred remains and ashes left behind are that part of the wood that is other than phlogiston, called the calx (sounds a bit like a dusty death cough, doesn’t it? or perhaps some mineral, or the beginning of a word – say, caloric – interrupted by death). Air can only hold so much phlogiston, however; if you burn something in a sealed vessel, it will burn out before it is all burnt, because the air has become saturated with phlogiston, and phlogiston will flow just in quantities that can be absorbed.
Well, yes, we all know better now. But the things we all have learned in school about molecular vibration and reactions and so on are really much advanced beyond the state of understanding of the 1700s. And even through the 1700s, the state of understanding was advancing; by 1800, pretty much no one still believed in phlogiston. No, heat was obviously a completely massless substance called caloric…
A lot of us won’t even know how to pronounce phlogiston now – it’s like “flow jist on” (if you want to say it like “floggy ston,” well, for shame! that would be closer to how the ancient Greeks said it, and what did they know?). But we will all get the fact that the ph is really a /f/. That matches a pattern of adding h to the letter for a stop to indicate a fricative near the stop: th for the fricative closest to /t/, and kh or ch to indicate one close to /k/. We also use it to shift the fricative /s/ towards the palate, sh. But there are two questions: a) why only those letters, and b) why bother with ph when we have f ?
Indeed, we note that we don’t use bh to spell /v/. Well, actually we do, in a few names borrowed from Gaelic, notably Siobhan; Gaelic doesn’t have the letter v. We also don’t use dh to spell the voiced pair of th; we use th for both. In fact, we used to have two completely different letters, eth (ð) and thorn (þ), which came to be used interchangeably to stand for either sound, and then were discarded under European (especially French) influence, especially when the English started buying their moveable type from Europe. The available replacement orthography in European style was th only. Most European languages don’t even have the voiced dental fricative (as in the); Classical Greek didn’t, though modern Greek does (in place of /d/). As to gh, well, we no longer make that sound anyway… but, ironically, we do still write gh where we used to make it.
And why not just write f ? Italians do – philosophy in Italian is filosofia – and in the earlier 20th century the New York Times took it upon itself to lead the charge for a similar change, writing, for example, filosofy. It obviously didn’t take. But the Latins, who also had f, used ph when transliterating the letter phi (φ) from Greek (there are plenty of Greek loan words in Latin). That was because in the Greek of the time it was like a /p/ followed by a bit of /h/ – actually the same sound we say at the beginning of pit (compare with spit, where the light puff of /h/ is absent). Now we retain it as a sort of charming archaism, smacking of science – or sometimes of what used to be thought of as science. Or, of course, of pseudo-scientific satire and other hip (or should I say phat) things.