In the Little House on the Prairie TV show, Laura and Almanzo have nicknames for each other – Manly and Beth. And for those who watched most of the series with Laura known as Laura, her character being referred to suddenly as Beth can be confusing.
In real life, the real Almanzo actually called Laura by the nickname Bess. Bess was after Laura’s middle name Elizabeth. Almanzo’s older sister was named Laura, so he began calling Laura by the Bess nickname instead.
It is not known for certain why the television show decided to change Laura’s nickname from Bess to Beth, except for the reason that Beth is a much more common name than Bess today.