Ahithophel in Smiths Bible Dictionary

(brother of foolishness), a native of Giloh, was a privy councillor of David, whose wisdom was highly esteemed, though his name had an exactly opposite signification. 2Sa 16:23 (B.C. 1055-1023.) He was the grandfather of Bathsheba. Comp. 2Sa 11:3 with 2Sam 23:34 Ahithophel joined the conspiracy of Absalom against David, and persuaded him to take possession of the royal harem, 2Sa 16:21 and recommended an immediate pursuit of David. His advice was wise; but Hushai advised otherwise. When Ahithophel saw that Hushai's advice prevailed, he despaired of success, and returning to his own home "put his household in order and hanged himself." 2Sa 17:1-23

Link: https://bible-history.com/smiths/A/Ahithophel/