Zainab's original name was "Barrah," but it was said' "By that she is giving herself the prestige of piety." So the Prophet (ﷺ) changed her name to Zainab.
Sahih al-Bukhari Book 78, Hadith 216
← Previous Hadith When Al-Mundhir bin Abu Usaid was born, he was brought to the Prophet (ﷺ) who placed him on his thigh. While Abu Usaid was sitting there, the Prophet (ﷺ) was busy with something in his hands so Abu Usaid told someone to take his son from the thigh of the Prophet (ﷺ) . When the Prophet (ﷺ) finished his job (with which he was busy), he said, "Where is the boy?" Abu Usaid replied, "We have sent him home." The Prophet (ﷺ) said, "What is his name?" Abu Usaid said, "(His name is) so-and-so. " The Prophet (ﷺ) said, "No, his name is Al-Mundhir." So he called him Al-Mundhir from that day.

Sahih al-Bukhari Book 78, Hadith 215 Next Hadith → That when his grandfather, Hazn visited the Prophet (ﷺ) the Prophet (ﷺ) said (to him), "What is your name?" He said, "My name is Hazn." The Prophet (ﷺ) said, " But you are Sahl." He said, "I will not change my name with which my father named me." Ibn Al-Musaiyab added: So we have had roughness (in character) ever since.

Sahih al-Bukhari Book 78, Hadith 217