Lord Brahma wanted to do a Yagna. He did it without his wife Saraswathi. So she got angry and wanted to spoil the Yagna and came running with full force as a River. As brahma requested Lord Vishnu to protect his Yagna, he went and lay in front of the fiery river and Saraswati being a woman was taken aback by the form of a man lying in her path and she was overcome with the feeling of shyness, since she was overcome by the feeling of shyness she lost her anger. This is depicted by the humbled Saraswathi Devi is seen at the foot of the resting Lord (Vishnu Sethu) with folded hands.
Since, the force (Vegam) is reduced by him, he is called Vega Sethu. This is the name of the Urchavamoorthy, we see in the Pic.
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