How Hawaii got its nickname?
you don't need to know this so just let it go and use google.
In the original Hawaii 5-0 (1968-80) Danny grew up in Hawaii, went to the University of Hawaii, and Danno was his Hawaiian nickname. In the new Hawaii 5-0, Danny comes from New Jersey, and it is his daughter, Grace, who gives him the nickname Danno. The others use it to make Danny irritated, as would happen in any family group.