🔼The name Nethinim in the Bible
Whether the name Nethinim is actually a name appears to be disputed. The old-school translations (Jewish Society Publication (1917), American Standard Version, Darby, Young) seem to think so, but the more modern translations (New American Standard, New International Version) don't, and consistently speak of "temple servants" (and the King James consistently speaks of Nethinims, which erroneously stacks an English plural on top of a Hebrew plural; it's either Nethins or Nethinim; also note that, for some obscure reason, the NAS has Nethinim in Ezra 7:24).
It seems a bit silly to only translate this particular name, and not any of the other semi-names that are really rather titles or epithets, such as Christ or satan. But on the other hand, most translations translate the name Qoheleth, which is probably also rather a title than a personal name. And the word kohanim is consistently and correctly translated with "priests," so it's not all that odd that translators give their readers their interpretation of the word Nethinim. The question is: what interpretation should that be? And isn't the word "priest" in fact as abstract as the Hebrew word kohen, when we are not familiar with this priest's religion and we have no clue what his duties are or even what defines him as a priest?
The Nethinim are introduced in the Bible in 1 Chronicles 9:2, where they are mentioned in one breath with the returning Israelites, the priests and the Levites, so it seems obvious that these Nethinim hold a religious office of some sort. Our modern religious institutions usually have priests or ministers, and general Levites could perhaps be compared with a modern church's staff, but the office of the Nethinim appears to have no modern counterpart.
A similar structure occurs in the books of Ezra and Nehemiah. Ezra and Nehemiah introduce the home-comers and first lists the leaders (Ezra 2:2, Nehemiah 7:7), then the Israelites at large (Ezra 2:3-35, Nehemiah 7:8-38), then the priests (Ezra 2:36-39, Nehemiah 7:39-42), then the Levites (Ezra 2:40-42, Nehemiah 7:43-45) and then the Nethinim (Ezra 2:43-58, Nehemiah 7:46-60; and note the substantial number of these Nethinim that are mentioned by name, although some of this list are not proper Nethinim but descendants of Solomon's servants, which apparently was yet another class).
Apparently, these Nethinim had their own cities, as the Levites did (1 Chronicles 9:2, Ezra 2:70, Nehemiah 7:73); Nehemiah mentions one, namely Ophel (Nehemiah 3:26), which was governed by two individuals named Ziha and Gishpa (Nehemiah 11:21). But the Nethinim also had their own designated hide-out somewhere along the wall of Jerusalem, close to a warehouse of sorts. Nehemiah reports that a goldsmith named Malchijah repaired the wall "as far as the house of the Nethinim and of the merchants" (Nehemiah 3:31).
Nehemiah 7:73 and Ezra 7:7 list the Nethinim along with, again, the Israelites, the priests and the Levites, but also with the singers and the gatekeepers. Ezra 7:24 even proclaims exemption from taxes for all priests, Levites, singers, doorkeepers, Nethinim or "servants of this house of God," which pretty much tells us that the Nethinim weren't priests or Levites but also no singers, gatekeepers and couldn't even be considered servants.
Ezra 8:17 tells of a contingent that Ezra sends to Iddo and his brothers the Nethinim, to give them ministers for the newly repaired temple. Ezra 8:20 mentions 220 of the Nethinim whom David and some princess had given for the service of the Levites. So it seems that the priests ran the temple business, the regular Levites served the priests and the Nethinim served the Levites.
And from Ezra's dealings with Iddo, it even seems that the Nethinim were some kind of proto-Levites, maybe trainees or cadets. Perhaps Israelites at large, who obviously couldn't be Levites, were allowed to be Nethinim, and proper descendants of Levi had to be Nethinim for a while before they could call themselves working Levites. But that's all conjecture.
🔼Etymology of the name Nethinim
The name Nethinim is a plural form derived from the verb נתן (natan) meaning to give:
Whatever their duties were, or whatever the practical purpose of their office, the Nethinim appear to have originated from a being given to God (of children by their parents). Giving one's children to the deity was a common practice in the Levant, although in the pagan parallels the child wouldn't survive the sacrifice (see our article on Molech). A child given to YHWH — the Lord of Life — on the other hand, would live a rewarding life in His service. An obvious example of such a Given One is Samuel, whose mother Hannah promised him to the Lord before he was conceived (1 Samuel 1:11). Samuel became an apprentice and later a priest and finally the last judge of Israel.
The name Nethinim means Given Ones. Neither NOBSE Study Bible Name List nor Jones' Dictionary of Old Testament Proper Names treat this name. BDB Theological Dictionary features a tiny article on the Nethinim and interprets the name as ("probably") Those Given "to the service of the sanctuary".