If a name is partially legible in a document or record, it can be difficult to find a list of names that “it could be.” One way to potentially get a list is to search a database for those known letters using a wildcard search. If a maiden name in a church marriage register looks like Tr[letters]t[letters]n, search for Tr*t*n in databases that contain name from the same general area where the name you are unable to read comes from.
Using databases on Ancestry.com, FamilySearch, etc. are great ones because if the record set is a large one, you are pulling from a large group of names. When performing searches of this type, search specific databases. If the name is of German origin, focus on databases from that area. If it’s English, use indexes to English parish records or other English materials.