What does HUH stand for?

Huahine - French Polynesia - Airport symbol (OAG)

Hualalai - Hawaii - Seismograph station code, US Geological Survey (SEIS)

Huilliche - Language code (ETLW)

Hunters Hide Boats, Huntington Station, NY - Manufacturer code for watercraft hull identification number (USCG)

University of Hawaii, Hamilton Library, Honolulu, HI - OCLC symbol (OCLC)