If you dont want to type the word "Humuhumunukunukuapua`a" each and every time and you want to use the abbreviation, use the following command
:set abb Humuhumunukunukuapua`a
:una 9u Humuhumunukunukuapua`a
:ab 9u Humuhumunukunukuapua`a
None of the above