The other day I was wondering, for no particular reason, why it is that a person who does astrology is called an astrologer, whereas a person (such as myself) who specializes in cosmology is a cosmologist.
Before proceeding to bore you further I will point out: (i) that words such as astrologer or cosmologist are examples of “noun of agency” or “agentive nouns” as they denote the agent or doer of an action; and (ii) that the suffix “-ology” signifies the study of a particular subject of thing. The word “ology” itself has come to mean “a branch of study” (at least informally).
Most ologies have an agentive noun that ends in “ologist”. As well as cosmologist, we have biologist, geologist, anthropologist, sociologist, and so on. There’s even “apologist” although I don’t think “apology” is an ology in the usual sense. Astrology is an ology, but we don’t usually talk about astrologists. In fact I rarely talk about astrologers either, but that’s not the point.
Looking in various dictionaries, however, I do see that the “-ologer” ending is given for some of the ologies listed above, including “geologer” but in all cases that I’ve found these are marked as archaic. Perhaps “astrologer” has lingered because astrology is a subject that likes to present itself as having ancient credentials.
There is another exception to the “ology-ologist” rule. At least in English English, a person who studies theology is not a theologist, nor even a theologer, but a theologian. I don’t know how that came about. There are quite a few people who can’t resist mixing religion with science when they talk about the field of cosmology, so perhaps cosmologian might be an appropriate term for them?
In the Dark 