The Catholic Encyclopedia
This is the ordinary form of the name in the English Bible; it corresponds better to the Hebrew Haggith, "Festive", than Aggith, as the name is spelled in 1 Chronicles 3:2. Haggith was one of David's wives (2 Samuel 3:4). Whose daughter she was, we are not told. The Bible records only that she bore to him Adonias, the fourth of his sons, in Hebron, before he was king over all Israel. That she was an uncommonly remarkable woman, seems to be suggested from the custom of Biblical writers to speak usually of Adonias as "the son of Haggith". Although harem intrigues have ever played a great part in the East, nothing indicates, however, that Haggith had anything to do either with the attempt of her son to secure for himself the crown of Israel (1 Kings 1:5-53), or with his fatal request, likely also prompted by political motives, to obtain his father's Sunamite concubine, Abisag, from Solomon (1 Kings 2:13-25).
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Obstat, Nihil. Lafort, Remy, Censor. Entry for 'Haggith'. The Catholic Encyclopedia. https://www.studylight.org/encyclopedias/eng/tce/h/haggith.html. Robert Appleton Company. New York. 1914.