To my limited understanding; there were a few "hush-puppy" rounds & service pistols developed/R&Ded for the MAC-V-SOG or Special Operations Group and few USMC Force Recon/SEAL-UDT units deployed "down range".
Retired US Army officer(Major/0-4/USAR) John Plaster who was a former member of a MAC-V-SOG team(normally three GIs & 5-6 hired mercs) wrote a few articles/books about the use of High Standard, Ruger & Hi-Power/P35s converted to suppressed weapons.
USAF veteran & top EP agent; Leroy Thompson wrote at length about the hush-puppy pistols of SE Asia too. I don't recall any 1911s or 1911a1 .45acp models but I have seen Browning Hi-Powers in 9x19mm with sound surpressors in use with special forces/MAC-SOG & SEALs/UDT.
The term means to quietly dispatch guard dogs with a clean pistol shot(.22LR or 9mm).