For years, I have been familiar with the phrase "incertae sedis." Actually, I've been familiar with the phrase "fragmenta incertae sedis," or sometimes "incertae sedis fragmenta." (Rules about word order are much more flexible for Latin than for English.) It means, roughly, "fragments of uncertain position," and as I've seen the phrase used, it refers to fragments of Greek or Latin, about which an editor is not entirely certain how to categorize them.
For example, in the 1990 Oxford Classics edition of Hesiod by Solmsen, Merkelbach and West, pp 213-219 contain fragmenta incerta sedis, fragments, in this case all in the form of passages from other ancient authors, which may or may not contain material originally written by Hesiod.
But the reason I'm writing this post is because I just found out today that the phrase "incertae sedis" in used in taxonomy to indicate that it is uncertain where exactly an organism stands in relation to other organisms. For example, the California condor used to be placed incertae sedis within the class Aves (birds), before the order Cathartiformes was recognized, which now includes that condor.
Well, the fact that "incertae sedis" is used in taxonomy is part of the reason I'm writing this. Another part is that I get the strong impression that many taxonomists do not know that the phrase has also been used for a very time in Classical studies. I'm not upset with taxonomists for not knowing this, no more than I'm upset because many or most Classicists may be unaware of how the phrase is used in taxonomy. I just find it interesting that the phrase exists in frequent use in these two separate fields, and I wonder about the phrase's history, and in what other fields it may have been used, or may continue to be used.
One thing which does upset me is knowing that some people find such subjects so intensely boring that 5 words' worth of posts like this causes them actual physical pain. I don't want to hurt anyone. I regret having rattled on and on to family and friends about such things for years and years before realizing how boring I was. I want to make other people see the fascination in such linguistic things, and it upsets me that I don't know how to make them interested, how to bridge that gap between them being so bored that it physically hurts, to where I and a few other people are, so fascinated by the very same subjects that my toes are curling with pleasure as I write this and wonder about the history of the phrase "incertae sedis."
(By the way, I also found out that the term "taxonomy" is used in other fields besides biology!)