Some nouns that end with O are:
a three letter word is bug. Three letter words ending with the letter g are bug and hug.
The three-letter word for scull is "oar."
A three-letter word ending in "ux" is "lux," which means a unit of illumination or light.
boa
who
Some three letter words ending in AT are:batcateatfathatmatpatoatpatratsattatvat
too
eta
you, emu, gnu
suq
imp
fra