The German word for 'slip(s) of paper'; and the title given (even in English) to a book of
remarks by
Wittgenstein, constructed by his posthumous editors out of many slips of paper in a
box file he kept.
Wittgenstein actually left an enormous amount of material in various degrees of disorganization. What they could, his editors (foremost of whom being G.E.M. Anscombe) fitted in Part II of Philosophical Investigations; others formed recurrent observations on logic and grammar, on psychology, and on certainty; and these could be incorporated into separate books.
Zettel represents a large number of thoughts that Wittgenstein grouped together in various ways but which do not obviously form a coherent whole. As they finally published it, there are 717 numbered remarks in it.
Most of the remarks date from 1945-8, with a few going back to 1929, when he began his radical repudiation of his earlier philosophy. Anscombe and G.H. von Wright created the arrangement, and Anscombe is its English translator. It was published in 1967. (Wittgenstein died in 1951.)