What does Genesis 35:18 mean?

Rachel was the woman Jacob desperately loved and worked hard for, though he was tricked into also marrying her sister, Leah (Genesis 29:30). After years of being barren, Rachel finally gave birth to a son, who she named Joseph (Genesis 30:24). That name, itself, was a prayer for more sons. Whether or not Rachel gave birth to any daughters after Joseph, Scripture does not say. Years later, as Jacob's family relocates, Rachel goes into a state of extremely intense, difficult labor. The midwife is able to reassure Rachel that she's just had another son (Genesis 35:16–17).

Sadly, the birth of this boy will end Rachel's life. With her dying breath, she imparts a name on the boy: Ben-oni, which most likely means "son of my sorrow" or "son of my pain." Jacob rejects this name, choosing instead the name Binyāmin', transliterated in English as Benjamin, meaning "son of the right hand." The exact reason why Jacob rejects his wife's dying words is not stated. Perhaps he didn't wish to leave the reference to sorrow in his son's name.