Conversation so far:
who wrote don't judge a book by its cover
The phrase is attributed to a 1944 edition of the African journal American Speech: “You can't judge a book by its binding.“
who popularized the saying don't judge a book by its cover
It was popularized when it appeared in the 1946 mystery Murder in the Glass Room by Lester Fuller and Edwin Rolfe: “You can never tell a book by its cover.”

Question: how about the saying to butter someone up
Self-contained rewrite: who popularized the saying to butter someone up