Thanks GJ I'm hoping you can guess this one before I have to take off for work. If not, I'll turn it over to you or anyone else who'd like to host during the day.
comas--oo
comma--xx
aroma--xxo
edema--xx
I think Plasmid was referring to the big S on Superman's chest. And many salt shakers will also have an S on the outside to help distinguish the salt shaker from an identical pepper shaker/mill.