Laura Ingalls had a special nickname for Almanzo, Manly. Many of his family and friends called him Manny, but Laura misunderstood him the first time she heard his nickname and then said she preferred the name Manly, as Manny (also referred to as Mannie by Nellie Oleson in These Happy Golden Years) sounded silly to her.
The name Manly was used in The First Four Years, although he was referred to as Almanzo by Laura in the rest of the Little House books.
This is one of the similarities between both the books and the television show because the nickname Manly was used in both. However, while the real Almanzo called Laura the nickname Bess, in the television show it was changed to Beth instead.