In Egyptian mythology, Hu is the god of the word which Ra used to create the world (and is also the word itself). He, and Sia, were created from a drop of blood that came from Ra's penis. They both represent the mind and wisdom of Ra.
Hu also is referred to by the ancient Egyptians as the "divine utterance". As such it is analogous to Christianity's logos, the Om of Hinduism, etc.
In Egyptian mythology the creating word of the sun-god of Heliopolis, personified in the same god.
With Sia he forms a primeval pair, both born from a drop of blood from the penis of Re, and together the personify the insight and wisdom of the sun-god.
When the pharaoh became a lone star, his companion was Hu.