LN: Occupational surname
SO: FN is four syllables. MN is an unusual word name.
SO: FN is in the top 200 of this list
http://www.behindthename.com/top/lists/us/1880. MN begins with X, Y or Z.
DD: FN is a geographical/location name. MN is a palindrome.
DS: FN is an uncommon biblical name. MN is shared with a football player (soccer)
DD/DD: FNs are flowers. MNs are anagrams of each other.
DS: FN has a an animal meaning. MN is a classic.
DS: FN ends in A. MN is from this list
http://www.behindthename.com/top/lists/no/2013DD: FN is from a song title. MN is Irish.
DS/DD: FNs are long but have 'cute' NNs. MNs begin with the same letter as FNs.
DS: FN one syllable. MN is 9+ letters.