A psaltery is more or less a generic term for a type of musical instrument that consists of strings mounted on a wooden board, and tightened by pegs. Every major culture in history has developed a psaltery or one sort or another, and it is clearly thousands of years old. For instance, the hammer dulcimer is a psaltery played by striking, and arose in the Middle East more than 3,000 years ago. You can read some more about the history of the psaltery.