Every word of God proves true; he is a shield to those who take refuge in him.
Proverbs 30:5 ESV

This is the essence of what it means to "Believe in the name of God": To believe that every word of his is true and to take refuge in him.

It's not enough to believe that God can forgive your sins by the blood of Yeshua. It's not enough to believe that Yeshua really came in the flesh and died for our sins. You have to believe IN him, which means you trust that every word he tells you is true, including the parts you don't want to hear.

Psalms 7:11-13 ESV
God is a righteous judge, and a God who feels indignation every day.
If a man does not repent, God will whet his sword; he has bent and readied his bow;
He has prepared for him his deadly weapons, making his arrows fiery shafts.