Concise Bible Dictionary:

Name, signifying “given, devoted ones,” applied to those who assisted the Levites in the service of the tabernacle and the temple. The name does not occur until 1 Chronicles 9:22Now the first inhabitants that dwelt in their possessions in their cities were, the Israelites, the priests, Levites, and the Nethinims. (1 Chronicles 9:2), and afterward in Ezra and Nehemiah. The Gibeonites were made “hewers of wood and drawers of water for the congregation and for the altar” (Josh. 9:2727And Joshua made them that day hewers of wood and drawers of water for the congregation, and for the altar of the Lord, even unto this day, in the place which he should choose. (Joshua 9:27)). These are not mentioned after 2 Samuel, so that they and their descendants may have been the “Nethinim.” It does not appear that God appointed them, as He did the Levites, but “David and the princes” appointed them “for the service of the Levites” (Ezra 8:2020Also of the Nethinims, whom David and the princes had appointed for the service of the Levites, two hundred and twenty Nethinims: all of them were expressed by name. (Ezra 8:20)). Some of the Midianite captives were also given to the Levites (Num. 31:46-4746And sixteen thousand persons,) 47Even of the children of Israel's half, Moses took one portion of fifty, both of man and of beast, and gave them unto the Levites, which kept the charge of the tabernacle of the Lord; as the Lord commanded Moses. (Numbers 31:46‑47)). After the return from exile the Nethinim are called the “ministers of this house of God.” They were, along with the priests and Levites, exempt from “toll, tribute, or custom” (Ezra 7:2424Also we certify you, that touching any of the priests and Levites, singers, porters, Nethinims, or ministers of this house of God, it shall not be lawful to impose toll, tribute, or custom, upon them. (Ezra 7:24)). A list of them is given in Ezra 2:43-5443The Nethinims: the children of Ziha, the children of Hasupha, the children of Tabbaoth, 44The children of Keros, the children of Siaha, the children of Padon, 45The children of Lebanah, the children of Hagabah, the children of Akkub, 46The children of Hagab, the children of Shalmai, the children of Hanan, 47The children of Giddel, the children of Gahar, the children of Reaiah, 48The children of Rezin, the children of Nekoda, the children of Gazzam, 49The children of Uzza, the children of Paseah, the children of Besai, 50The children of Asnah, the children of Mehunim, the children of Nephusim, 51The children of Bakbuk, the children of Hakupha, the children of Harhur, 52The children of Bazluth, the children of Mehida, the children of Harsha, 53The children of Barkos, the children of Sisera, the children of Thamah, 54The children of Neziah, the children of Hatipha. (Ezra 2:43‑54); Nehemiah 7: 46-56,60; Nehemiah 10:2828And the rest of the people, the priests, the Levites, the porters, the singers, the Nethinims, and all they that had separated themselves from the people of the lands unto the law of God, their wives, their sons, and their daughters, every one having knowledge, and having understanding; (Nehemiah 10:28).

Jackson’s Dictionary of Scripture Proper Names:

given ones

From Manners and Customs of the Bible:

These were men who assisted the Levites in performing the meanest offices connected with the temple service. Part of them lived in Jerusalem, and part were distributed among the Levitical cities. They are supposed to have been Canaanites reduced to servitude (Josh. 9:21-2721And the princes said unto them, Let them live; but let them be hewers of wood and drawers of water unto all the congregation; as the princes had promised them. 22And Joshua called for them, and he spake unto them, saying, Wherefore have ye beguiled us, saying, We are very far from you; when ye dwell among us? 23Now therefore ye are cursed, and there shall none of you be freed from being bondmen, and hewers of wood and drawers of water for the house of my God. 24And they answered Joshua, and said, Because it was certainly told thy servants, how that the Lord thy God commanded his servant Moses to give you all the land, and to destroy all the inhabitants of the land from before you, therefore we were sore afraid of our lives because of you, and have done this thing. 25And now, behold, we are in thine hand: as it seemeth good and right unto thee to do unto us, do. 26And so did he unto them, and delivered them out of the hand of the children of Israel, that they slew them not. 27And Joshua made them that day hewers of wood and drawers of water for the congregation, and for the altar of the Lord, even unto this day, in the place which he should choose. (Joshua 9:21‑27)) and captives taken in war, who were set apart to this service, and therefore called nethinim: the given, the devoted. They were held in low esteem by the Jews, occupying a social position even lower than the rammer or illegitimate offspring.