What does Ygritte mean by shades?

Question

In A Storm of Swords, Ygritte, some other wildlings and Jon Snow climb the wall. As they stand atop the wall, she starts crying and tells Jon that they searched for the Horn of Joramun to bring down the wall and they dug many graves. Finally she said:

We opened half a hundred graves and let all those shades loose in the world 

What does she mean by shades? Surely they can't be the Others as Craster has been giving his sons to the Others way long before they started digging the graves. What are these shades Ygritte has mentioned?

Answer 1

I believe the simple answer is using the term "shades" to mean "ghosts".

shade: literary A ghost.

This makes sense in context as they are opening graves and therefore letting the ghosts of the dead back into the world.

Shade is used to refer to ghosts/spirits of the dead elsewhere in the books.

And yet, he knew he could not keep silent. He had a duty to Robert, to the realm, to the shade of Jon Arryn … and to Bran, who surely must have stumbled on some part of the truth. Why else would they have tried to slay him?

_{A Game of Thrones - Eddard XII}

Ser Rodrik said, "That would please the Glovers, and perhaps Lord Hornwood's shade as well, but I do not think Lady Hornwood would love us. The boy is not of her blood."

_{A Clash of Kings - Bran II}

"King Renly's shade was seen as well," the captain said, "slaying right and left as he led the lion lord's van.

...

Renly's shade. Davos wondered if his sons would return as shades as well.

_{A Storm of Swords - Davos II}

In the above reference we know all those characters to be dead so therefore would be shades. I feel the last Davos quote is most telling in this regard as it mentions the direct reference to the dead returning as shades.

Also, as a point of clarity as I'm not sure with your phrasing "and they dug many graves", they were not digging new graves but opening old ones back up to see if the horn had been buried.

Answer 2

She is meaning they let their spirits loose, a shade is:

In literature and poetry, a shade (translating Greek σκιά, Latin umbra) is the spirit or ghost of a dead person, residing in the underworld.

We see this has come up before referring to Lady after her death:

Summer's howls were long and sad, full of grief and longing. Shaggydog's were more savage. Their voices echoed through the yards and halls until the castle rang and it seemed as though some great pack of direwolves haunted Winterfell, instead of only two... two where there had once been six. Do they miss their brothers and sisters too? Bran wondered. Are they calling to Grey Wind and Ghost, to Nymeria and Lady's Shade? Do they want them to come home and be a pack together?

_{A Clash of Kings, "Bran I"}