The word "stave church" is unknown in Old Norse, presumably because there were no other types of wooden churches. When Norway's churches after the Reformation were constructed in log, there was a need for a separate word for the older churches. In written sources from the Middle Ages, there is a clear distinction between "stafr" (posts) and "þili" or "vægþili" (wall boards). However, in documents from the 1600–1700s, "stave" was also used for wall boards or panels. Emil Eckhoff in his "Svenska stavkyrkor" (1914–1916) also included wood frame church buildings without posts.