6 letter words:
soffit12,
5 letter words:
stiff11,
tiffs11,
toffs11,
foist8,
4 letter words:
offs10,
tiff10,
toff10,
fist7,
fits7,
sift7,
soft7,
3 letter words:
iff9,
off9,
fit6,
ifs6,
oft6,
its3,
sit3,
sot3,
tis3,
2 letter words:
if5,
of5,
is2,
it2,
oi2,
os2,
si2,
so2,
ti2,
to2,
