The idea of Masonic brotherhood probably descends from the 16th-century legal definition of a "brother" as 1 that has taken an oath of mutual help to another. Accordingly, Masons swear at each diploma to help keep the contents of that diploma top secret, also to guidance and protect their brethren https://ewr1.vultrobjects.com/blissdrive/westhillmasonry/Hardscape-Contractors.html