Bronze Kartikeya was Rudraansh. He himself was born from Shiva. Who is Shiva. Shiva the unborn who is personification of pranav. Means om. Once lord Brahma was chanting the Vedic mantra without invoking omkar. Lord kartikeya imprisoned lord Brahma with just chanting om. Lord Brahma cried for help. Lord Shiva asked lord kartikeya to release Brahma. Lord kartikeya said. Lord Brahma needs to understand the omkar.first. then Shiva asked lord kartikeya. Oh beloved son. Do explain it. Then lord kartikeya said you should first take me as your guru. Then lord Shiva set down and then lord kartikeya gave gupta gyan of omkar to lord Shiva. Hence Devi parvati gave lord kartikeya new name Swami natha. Means guru of my husband or guru of lord. This incident was created by lord Shiva himself to show the importance of omkar.