The word Prishni includes food, the Vedas, water, and nectar. These four are always in my stomach. Hence am I called Prishnigarbha.
पृश्निरित्युच्यते चान्नं वेद आपोऽमृतं तथा। ममैतानि सदा गर्भः पृश्निगर्भस्ततो ह्यहम्॥