Han gjorde inte
I böckerna säger Jeor uttryckligen att svärdet var kvar till sin son Jorah när han tog svart, bara att Jorah lämnade det när han flydde. När Jorah lämnade återvände Jeors syster det tillbaka till honom, men Jeor gömde bort det.
"It is," the Old Bear told him. "It was my father's sword, and his father's before him. The Mormonts have carried it for five centuries. I wielded it in my day and passed it on to my son when I took the black."
He is giving me his son's sword. Jon could scarcely believe it. The blade was exquisitely balanced. The edges glimmered faintly as they kissed the light. "Your son—"
"My son brought dishonor to House Mormont, but at least he had the grace to leave the sword behind when he fled. My sister returned it to my keeping, but the very sight of it reminded me of Jorah's shame, so I put it aside and thought no more of it until we found it in the ashes of my bedchamber. The original pommel was a bear's head, silver, yet so worn its features were all but indistinguishable. For you, I thought a white wolf more apt. One of our builders is a fair stonecarver."
A Game of Thrones, Jon VIII
Scenen i showen är mindre detaljerad om än i samma situation.
Jeor Mormont: It was my father's sword, his father before him. The Mormonts have carried it for five centuries. It was meant for my son Jorah. He brought dishonor to our House, but he had the grace to leave the sword before he fled from Westeros.
Game of Thrones, Season 1 Episode 9, "Baelor"
Varför höll han svärdet när Maege återvände svärdet till Jeor istället för att hålla det på Bear Island med huset, vi vet det inte bra. Det kan bero på att hon inte har några söner, så tror att det borde vara i manlig besittning.