For many centuries English speakers who were afraid of getting dirty got along pretty well by saying something like “I’m afraid of getting dirty.” Similarly, if they were afraid of spirits, they’d tell their friends “I’m afraid of spirits.” There are plenty of other examples. They didn’t need any special words for their fears.
Anna Seward wrote a letter in 1803 that showed what was about to happen: “He is a very laconic personage, and has upon him the penphobia.” That’s an indication that sometime around the turn of the 18th century, the idea of naming specific fears as “phobias” began to get pretty popular. It wasn’t a new idea; “hydrophobia,” or fear of water; was first used in 1547 by Andrew Borde in The Breuiary of Helthe: “Hidroforbia..is abhorringe of water… This impediment doth come..of a melancoly humour.” But for many years, “hydrophobia” seems to have been the only fear called a “phobia” in English.
Seward, by the way, probably got “penphobia” wrong; she most likely meant “panphobia,” which is the fear of anything or everything. It was described in 1897 in T. A. Ribot’s “Psychology of the Emotions”: “There exist some observations on a vague but permanent state of anxiety or terror, which has been called panphobia, or pantophobia (Beard).” And in 1965, Lucy Van Pelt diagnosed Charlie Brown with pantaphobia in A Charlie Brown Christmas — and only charged five cents.
“Phobia” comes from Latin, which in turn borrowed it from Greek, where it was “phobe” (well actually it was “ϕόβος” in Greek, but there’s no need to go overboard about it). Besides, some readers may suffer from xenoalphaphobia, which would be fear of alphabets that aren’t native to you. That’s the way it is with “-phobia”; you can put practically anything in front of it to construct a word that means “fear of…”.
Another characteristic of phobia words is that the prefix is customarily either Latin or Greek. In fact sometimes there are both; in addition to “hydrophobia”, which is fear of water (from Latin), there’s also “aquaphobia”, which is the same thing, but uses a prefix from Greek. There isn’t really any reason why you couldn’t just use an English prefix to form a word like “pantsphobia” or “pineapplephobia,” but somehow if you don’t use Latin or Greek it just sounds silly.
The phobia industry really took off in the late 1700s. There was “aerophobia” (originally fear of fresh air or drafts, but now sometimes used for fear of flying), “pneumatophobia” (fear of spirits, or possibly just fear of air), bibliophobia (fear of books)…and then things began to get ridiculous. No, really, “catagelophobia” is the fear of being ridiculed. And since then the list of phobias has grown steadily. There’s even “phobophobia”, which is the “fear of fear.” Some phobias have not just two, but multiple names. The fear of cats, for example, is “felinophobia,” “ailurophobia,” “elurophobia,” “galeophobia,” and even “gatophobia.” But the “don’t use an English prefix” custom is so strong that nobody ever mentions “catophobia.” There doesn’t seem to be any mention of “etymologiphobia”, which would be fear of etymology, but it might be covered by either “gnosiophobia” (fear of knowledge) or “logophobia” (fear of words). Possibly the most self-referential phobia of all is “hippopotomonstrosesquipedaliophobia” — the fear of long words.
