SJM meaning in General ?

Justin Martyr (Greek: Ἰουστῖνος ὁ μάρτυς, romanized: Ioustinos ho martys; c. 100 – c. 165) was an early Christian apologist and philosopher.

Most of his works are lost, but two apologies and a dialogue did survive. The First Apology, his most well-known text, passionately defends the morality of the Christian life, and provides various ethical and philosophical arguments to convince the Roman emperor, Antoninus, to abandon the persecution of the Church. Further, he also indicates, as St. Augustine would later, regarding the "true religion" that predated Christianity, that the "seeds of Christianity" (manifestations of the Logos acting in history) actually predated Christ's incarnation. This notion allows him to claim many historical Greek philosophers (including Socrates and Plato), in whose works he was well studied, as unknowing Christians.

Justin was martyred, along with some of his students, and is venerated as a saint by the Catholic Church, the Anglican Church, the Eastern Orthodox Church, and the Oriental Orthodox Churches.