The tag scottish-book has so far been added to these three questions: 1 2 3.
The logic is stated in the comments on the first of these questions (combined and slightly edited):
The idea of introducing this tag was suggested by user95282 in this comment In fact, some problems from Lviv Scottish Book were posed by other users from other accounts (I know at least two such cases). He suggested to create a new tag "scottish-book", which indeed has more sense than "lviv-scottish-book", which of course can be recovered from the account of the Lviv Scottish Book. In fact during the history there existed at least three Scottish Books: the original Lwow "Scottish Book" (1935-1941) with 193 problems, The Wroclaw "New Scottish Book" (1946-1987) with 968 problems, and the "Lviv Scottish Book" (2014--??) which has at the moment 23 problems, written to MO + 2 solved (without inscribing to MO). So the tag "scottish-book" would be just an indication that the problem can have some relation to one of these 3 Scottish books.
I am not sure this is a good idea, for a couple reasons.
First of all, while there is some internal logic to adding the tag more generally than the single user's questions, it seems to be a solution looking for a problem: there are rather few questions of this category that could be usefully tagged this way (other than going through the userpage of Lviv Scottish Book), and in any case one can find all of them by performing a search for "Scottish book", so the tag does not seem to have much functional purpose.
Secondly, there has already been a recent editing spree on these questions to add links to an online version of the "Lviv Scottish Book", taking up some amount of space on the front page whenever this is done. Adding the tag just seems like another occurrence of the same.
Third, this is a meta tag, which does not actually give content about the mathematics of the post (but rather the metamathematics of where the question originated). It is my recollection that there is agreement these should be avoided, but I couldn't find a discussion of this in a quick search.