As three goddesses viz., the sky, the firmament and the water, ever worship that lord of the worlds, therefore he is truly calied Tryambaka.
तिस्रो देवीर्यदा चैव भजते भुवनेश्वरः। द्यामपः पृथिवीं चैव त्र्यम्बकश्च ततः स्मृतः॥