4 letter words:
bufo9,
fano7,
faun7,
bona6,
boun6,
buna6,
3 letter words:
fab8,
fob8,
fub8,
auf6,
fan6,
fon6,
fou6,
fun6,
oaf6,
ufo6,
abo5,
ban5,
boa5,
bon5,
bun5,
nab5,
nob5,
nub5,
oba5,
2 letter words:
fa5,
of5,
ab4,
ba4,
bo4,
ob4,
an2,
na2,
no2,
nu2,
on2,
ou2,
un2,