“Targum” (תַּרְגּוּם) is Aramaic for interpretation, translation, or version. Originally referring to a spoken translation of Tanakh into the language of the listeners, made by a meturgeman (מְתוּרגְמָן), a translator, Targum, the practice of delivering Scripture to the masses in their (our) own language, began around the end of the first century BCE. Word has it that translators sometimes inserted their own commentary (“interpretation”), embellishing the reading into a sort of devar Torah.
Writing down the translations was forbidden, initially so that the translator would not be reading from a text and thus confuse the congregation as to which was the “real” writing. Yet by the middle of the first century CE there were such writings extant. Later, the Babylonian Jews accepted the translations as a part of their studied writings. Soon, the only language translation referred to as “targum” was Aramaic, which had been the lingua franca when the practice began. Today, some Yemenite Jews still use the meturgeman.
The book of Ezra, which itself was written in both Hebrew and Aramaic with some Old Persian thrown in, mentions translated letters being sent to King Artaxerxes in chapter 4, using the root word under discussion (כָּתוּב אֲרָמִית וּמְתֻרְגָּם - written in Aramaic and translated), though the most interesting word in this passage is Artaxerxes’ name: אַרְתַּחְשַֽׁשְׂתְּ.
After the destruction of the Second Temple in 70 CE, as synagogues became more the venue of worship and study, Targumim were used more often to reach the public with the meaning of the readings. The meturgemanim at first inserted explanation to clarify their translations. As time went on, the translators launched more into the moral lessons, allegory, legends, etc., which were popular at the time. Thus the later Targumim reflect more sermon than just literal translation. It wouldn’t be until around the fifth century CE that the text was fixed for posterity. One of the better known such texts is the Targum of Onkelos, interpreting the Torah, with the final revision delivered in the third century.
There are no Targumim to the books of Daniel, Ezra and Nehemiah, possibly because they were written later and are already written partially in Aramaic.
There have been some Targum fragments found among the precious detritus of the Cairo Genizah. Among other studies, scholars have been studying them to compare the vocalized language at various times in history. Some of these fragments are poems meant to introduce special Torah readings. The Akdamut Millin (אַקְדָמוּת מִלִּין) (written some time between 1010 - 1090 CE) which is read on Shavuot is thought to be a similarly written poem, which has continued in our tradition. Other Targumim were among the Dead Sea Scrolls.
The newspaper of Rutgers University, the State University of New Jersey, is The Daily Targum, so named in 1866 on inspiration from University President William H. Campbell’s lecture to students on the original text of Tanakh, including Targumim.