This gaseous giant, this whirling mass of Hydrogen & Helium, was called by the ancients as Dyo Pitah ( Dyo - Heaven; Pita Father ). Dyo Pita became Jupiter.
As 1300 earths can be fit into Jupiter, he is the largest and hence the Sanskritists called him Brihaspati, Brihatam Tasya Esha Pathih iti Brihaspati.