Way back in Avengers: Age of Ultron, Natasha teased Clint and his wife Laura about naming their new baby after her. At the time, the baby wasn't born yet, so she called it little Natasha. When Laura did give birth, she and Clint had another boy, but they still honoured Natasha by naming him Nathaniel. In the aftermath of Black Widow's death, little Nathaniel's name is even more meaningful than it was before.