The story of the name, from the sources
In Lisan al-Arab, a she-camel khadajat when she gave birth before her time, yet the young was fully formed. Such a newborn is khadij, and Khadija is its feminine: one who came early, yet whole.
“born before its time, yet fully formed”
such a newborn is khadij; Khadija is its feminine
Lisan al-Arab · vol. 2, p. 248 · al-Sihah · vol. 1, p. 308
Before Islam, al-Zubayr ibn Bakkar says, Khadija daughter of Khuwaylid was called al-Tahira, the pure one.
الطاهرة
“Before the revelation she was called al-Tahira, the pure one”
al-Zubayr ibn Bakkar
al-Isaba · vol. 8, p. 99 · al-Tabaqat · vol. 8, p. 12
She is the Mother of the Believers, may God be pleased with her. Al-Waqidi writes: our scholars agree that the first to answer the Messenger of God, peace be upon him, was Khadija.
the first to believe
“Our scholars agree that the first to answer the Messenger ﷺ was Khadija”
Ibn Sa’d, al-Tabaqat · vol. 3, p. 15 · vol. 8, p. 13 · al-Isaba · vol. 8, p. 100
After she died, Aisha said, the Prophet would slaughter a sheep and send some of it to Khadija's friends. And in Sahih al-Bukhari, Gabriel, peace be upon him, said: convey to her the greeting of peace from her Lord, and from me.
“He would slaughter a sheep and send some of it to her friends”
Aisha
Gabriel: “Convey to her the greeting of peace from her Lord, and from me”
Sahih al-Bukhari 3816 · 3820