Al-Tabarani says: He is Sayyiduna Nu'aym (may Allah be pleased with him) bin Abdullah bin Asad bin Abd Awf bin Ubayd bin Uwayj bin Adi bin Ka'b. He was named "al-Nahham" because the Prophet (peace and blessings be upon him) said: "I heard a 'nahmah' in Paradise." The word "nahm" means "voice."
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15985