BCE0005: Unknown identifier: 'weaponName'.

Hi I am a beginner. I dont understand why weaponName cannot be Identified can someone help?
Here is my code, I am using Javascript.

function Update()
{

	if(Input.GetKeyUp("space"))
	{
			WeaponSearch();
	}

}

function WeaponSearch()
{

var	weapon = Random.Range(1, 6);


switch(weapon)
{
	case 1 :	
		weaponName = "Sword";
		DisplayMessage(weaponName);
		break;
	case 2:
		weaponName = "Axe";
		DisplayMessage(weaponName);
		break;
	case 3:
		weaponName = "Dagger";
		DisplayMessage(weaponName);
		break;
	case 4:
		weaponName = "Bow";
		DisplayMessage(weaponName);
		break;
	default:
		Debug.Log("You need to find a weapon!");	
	}

}

function DisplayMessage(weaponName)

{

Debug.Log("You found " + weaponName + “!”);

}

You’ve never declared the ‘weaponName’ variable in this script. At the top of the file (outside of any function) put:

private var weaponName : String = "";