Family loves playing the following game:
While I was visiting them it go me thinking that you could use the command lines built in dictionary.
And by using that you can use your trusty grep to find matches
grep -v '[^nossle]' /usr/share/dict/words | egrep -x '.{6,6}'
By doing an invert on a select of nots (in another words match words that have these letters) and then piping it into a fixed string length, you can get the answer:
lessee
lessen
lesson
loosen
nelson
nonene
oleose
seesee
snoose
sossle
e.g. lesson
So next time you see someone struggling, you have a little tool to help.