8 letter words:
coeffect18,
6 letter words:
coffee14,
effect14,
toffee12,
4 letter words:
coff12,
teff10,
toff10,
coft9,
ecce8,
ecco8,
feet7,
fete7,
cete6,
cote6,
3 letter words:
eff9,
off9,
eft6,
fee6,
fet6,
foe6,
oft6,
tef6,
cee5,
cot5,
eco5,
tec5,
toc5,
tee3,
toe3,
2 letter words:
ef5,
fe5,
of5,
ee2,
et2,
oe2,
te2,
to2,
