"Mitzpah" is the Hebrew word for watchtower. In the Bible, it symbolizes the emotional bond of two men, that the Lord may watch over to ensure that each honors his commitment to the other when parted.
The word is first seen in Genesis 31:49: "And Mizpah, for he said, The LORD watch between me and thee, when we are absent one from another." The passage makes for a popular sentiment for friends, family and lovers who are parted. As such, it commonly appears on necklace and bracelet charms that split down the middle to be shared between two people, forming halves that are only complete when reassembled. Such charms are called "Mizpah" as well.