Thuwaybah was the freed slave-woman of Abu Lahab. Abu Lahab had set her free, and she nursed the Prophet ﷺ.
وثويبة مولاة لأبي لهب، كان أبو لهب أعتقها. فارضعت النبي ﷺ.
Bukhari narrated it in the Book of Marriage (5101), and this is his wording, and Muslim narrated it in the Book of Suckling (1449), both of them through various routes from Urwa bin Zubayr, that Zaynab bint Abu Salama told him, and he mentioned the hadith in full.