I am not aware of any word that was used earlier, and there isn't really any strong 'more Polish' candidate to be used instead of "weekend".
I think that it may not have been a needed concept before. I don't know how it was before the war, but in the post-war communist Poland, Saturdays were normal work days. It started changing slowly in 1973 when first free Saturdays were introduced. It must have been around then when the English word started to be used.
Tak. Jellei. U r so correct. U r Brilliant!! That's why I think, Sunday- Niedziala, = no work referring to the biblical and to literal. 6 days of work and 1 rest day. (I forgot that school was on a Saturday in the old days). btw: I have a copy of Marlborough's SelfTaught Polish 1925.11th ed. - and there is no word for weekend in the 'Time and Season' vocab. It's so interesting how language and culture has changed. Thank you again.