As we mentioned earlier, kategor קטגור is a Talmudic term for "accuser, prosecutor". It appears as the opposite of praklit in Avot 4:13, and as the opposite of sanegor in Rosh HaShana 26a. Its verbal form - "to accuse, denounce" is קטרג, and developed through metathesis. In modern Hebrew neither is widely used, and instead we find the term (both verb and noun) tovea תובע for "prosecute, prosecutor".
Klein's etymology is:
We saw other words related to agora in the post about sanegor; kata, meaning "down, against", appears in such English words as catapult, catastrophe and catalog.
From Greek kategoros (= accuser; literally: "one who speaks against somebody before an assembly", from kata (= against), and the stem of agoreyein ( = to harangue, assert; literally: 'to speak in the assembly'), from agora (= assembly)
If the word kategor seems to you like the English word "category" (and the modern Hebrew word קטגוריה kategoria) - it's no coincidence. According to the Online Etymology Dictionary's entry for "category":
Original sense of "accuse" weakened to "assert, name" by the time Aristotle applied kategoria to his 10 classes of things that can be named.This site gives another possible path of development:
In ancient Greek "kategorein" is a concept of legal terminology and means the reading of a list of accusations performed in the process of charging someone.Horowitz (pg 268) has a note about the word kategor:
This word is clipped or rather shortened in the common idiom (kara tagar) -קרא תגר which means "call the prosecutor".I at first found this rather far-fetched. A slightly different form of tagar - tigra תגרה appears in Tehilim 39:11, and a related verb appears in Devarim 2:24, and these sources certainly wouldn't be influenced by the Greek kategor.
However, my sources tell me that there might be a connection between kategor and the development of the phrase kara tagar (if not the individual words.) If anyone knows about this - please post in the comments. Otherwise I'll update the post if I find anything.