"Son of the Widow" is one of the most significant titles in Freemasonry, particularly in the higher degrees. It refers specifically to Hiram Abiff, the master builder of Solomon's Temple, whose mother was a widow of the tribe of Naphtali according to 1 Kings 7:14. Hiram is the central figure of Masonic initiation — his murder before he could transmit the Master's Word, and the subsequent search for the lost word, structures the entire third degree and much of what follows in the higher degrees.
So a Master Mason, having undergone the ritual death and resurrection of Hiram, becomes symbolically a "Son of the Widow" — heir to the incomplete transmission, seeker of the lost word.
But the resonance goes deeper than Masonry. The title connects to a much older current in the tradition. In Gnostic and esoteric Christianity, the Sophia — divine Wisdom — is sometimes described as the widow, the divine feminine principle separated from her consort, wandering in exile. Her children — those who carry the divine spark and seek to return it to the light — are therefore Sons of the Widow in a cosmic sense.
The Cathar perfecti used this title. Some scholars trace it through various initiatory lineages back into the ancient world.