Right after Guam's recapture by American forces in 1944, the war against Japan was still in progress and U.S. military activities on Guam had to be kept under wraps. So, a code name for Guam had to be found and the military settled on Duva.
Guam was still called Duva by the military, perhaps informally, even after the war had ended.
A military club on Guam was called Club Duva Den.
Ceraminc drinking mugs from Club Duva Den
In the 1980s, I visited a Chamorro lady in Hawaii married to an ex-Marine who was stationed on Guam during or right after WW2. That's how he met and married his Chamorro wife.
When I'd walk into the door of their Waikiki condo, the ex-Marine husband would greet me with a "So how's things in Duva Duva?!?"