πρόσφορο = a (religious) offering
One of the problems in learning Greek is that a change in stress and/or word-ending can change meaning:
πεζοδρόμιο/πεζόδρομος/πεζοδρόμος = pavement/pedestrian precinct/walker or hiker;
διάδρομος/διαδρομή = hallway, aisle/itinerary, route.
In the same way, το πρόσφορο differs from η προσφορά, which means ‘an offer’ from the verb προσφέρω.
Interestingly, there is an adjective πρόσφερος – η – ο, which means ‘suitable’ or ‘useful’. It often collocates with έδαφος as in πρόσφερο έδαφος. Babiniotis states that it is a borrowing from the French ‘terrain favorable’. Word Reference translates it as ‘breeding ground’.
Specifically, το πρόσφορο is a small round loaf that the faithful bring to church. If I had to choose between parting with bread or spilling some beer, I would opt for the former. Fortunately, in modern Greece, the libation (σπονδή) – to the best of my knowledge – is no longer practised.