textbook (n.)youdaoicibaDictYouDict[textbook 词源字典]
also text-book, "book used by students," 1779, from text (n.) + book (n.). Earlier (1730) it meant "book printed with wide spaces between the lines" for notes or translation (such a book would have been used by students), from the notion of the text of a book being more open than the close notes. As an adjective from 1916.[textbook etymology, textbook origin, 英语词源]