Deep-seated source refers to a fundamental or deeply rooted origin or cause of something, often implying that it is entrenched and not easily changed.

गहराई से जड़ें जमाए हुए स्रोत

English Usage: The deep-seated source of his anxiety was his childhood trauma.

Hindi Usage: उसके तनाव का गहरे बैठे हुए कारण उसका बचपन का आघात था।