The Luminous Essence: A Guide to the Guhyagarbha Tantra says "This universal tantra of the great Magical Net is a secret among secrets".
Later it says:
Accordingly, mahāyoga teaches the complete nature of the ground, path, and fruition of the entire mantra vehicle. It is, therefore, essential to develop certainty regarding all aspects of mantra practice based on mahāyoga. Mahāyoga belongs to the inner tantras of secret mantra, and can itself be divided into an infinite number of categories. These all come about through the play of wisdom of the magical net.
Later they refer to "the wheel of the magical net." In several other places "magical net" is mentioned.
What is the magical net? Is that literally the etymology of "Guhyagarbha"? Searching the web reveals mayajala, but no insight is to be gained easily looking at that word.