In The Bronze Bow, what was the password Daniel and his friends used to talk about Romans?

Even though Daniel has moved to the village to take care of his sister, he has not given up on his desire to overthrow the Romans, and he has not renounced his allegiance to Rosh. He begins to build a band of young men in the village who will work in conjunction with Rosh. His first recruits are Nathan, Joel, and Kemuel. As they discuss recruiting additional members, they realize they can only take in people they can trust. When Nathan suggests they brand themselves to show they are all part of the group, Kemuel reminds them that making marks on their bodies is forbidden in the law. Joel then suggests that they "carry the sign of the bow in our minds." They will use the bow of bronze--a symbol Joel and Daniel have already claimed as representing God's victory--as their password. They agree and begin to use their code word to build solidarity among themselves. It gives them "pride and pleasure." Eventually the group grows to 21 boys who all crowd into Daniel's smithy--all committed to throwing off Roman oppression.