Parashas Pinchas · Passuk 27:21
And he shall stand before Elazar the Kohen, who shall inquire for him by the judgment of the Urim before Hashem; at his word they shall go out and at his word they shall come in, he and all the children of Yisrael with him, and all the congregation.
Chabad.org — 27:21
Torah Temimah: Yoma 73b
Sefaria — Yoma 73b
English: It was taught: why are they called Urim? Because they illuminate their words.
Etymology of Urim.
The name encodes clarity of the response.