Smith's Bible Dictionary
Adoni'kam or Adon'ikam. The sons of Adonikam, 666 in number, were among those who returned from Babylon with Zerubbabel. Ezra 2:13; Nehemiah 7:18; 1 Esdras 5:14 (B.C. 506-410). The name is given as Adonijah in Nehemiah 10:16.
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Smith, William, Dr. Entry for 'Adonikam'. Smith's Bible Dictionary. https://www.studylight.org/dictionaries/eng/sbd/a/adonikam.html. 1901.