What did Jesus mean by " many" beneficiaries of His ensuing blood-shed? At Matthew 26:27-28 (NRSVCE) we read:


  Then he took a cup, and after giving thanks he gave it to them, saying, “Drink from it, all of you;  for this is my blood of the covenant, which is poured out for many for the forgiveness of sins." 


Those words of Jesus are reproduced in the Eucharistic celebration of the Catholic Church. My question is: Why did Jesus use the words "for many" instead of  "for all"?  What are the connotations, including references to the OT, which the Catholic Church attribute to the word "many" as used by Jesus at the Last Supper?
In his Commentary on St. Matthew's Gospel, St. Thomas Aquinas writes:


  “He shall sprinkle,” meaning with His Blood, “many nations” (Is. 52, 15). For many, and for all, because if its sufficiency be considered, “He is the propitiation for our sins: and not for ours only, but also for those of the whole world” (I Jn. 2, 2). But if we consider its effect, it only has its effect on those who are saved, and this is the fault of men.


Although He redeemed everyone, not everyone's sins are forgiven; some people are damned due to their own fault.

Remigius explains it this way (quoted in St. Thomas's Catena Aurea on Mt. 26):


  And it is to be noted that He says not "For a few" nor "For all", but "For many"; because He came not to redeem a single nation, but many out of all nations.