Warning: Spoilers for Captain America: Civil War are in play. Bookmark this page, and come back after you've seen the movie, if you don't want to be spoiled.
In Captain America: Civil War, we learned that not only was Bucky kept in cryostasis between the dirty deeds HYDRA would wake him up to commit, but he also went through a rigorous mental conditioning to keep himself sharp. We saw the electromagnetic shock portion in Captain America: The Winter Soldier, but what we didn’t see was the fact that much like The Manchurian Candidate, Bucky was conditioned to respond to a special trigger that primed him to accept orders. In this case, the trigger was a series of 10 random words. But were they as random as we think?
Keep in mind, there’s still a chance that all, if not most, of these words are just interesting sounding words that are innocuous enough on their own that they wouldn’t raise suspicion. That said, we still feel breaking the list down word by word is the best way to find out if maybe this string of command words leads to some sort of deeper understanding into the psyche of Sgt. James Buchanan "Bucky" Barnes.
LongingGoing on pure symbolic grounds, "Longing" could represent the memories that Bucky tends to pick up on from his past life, right before he’s electro-shocked into his Winter Soldier state. We saw more of this in Captain America: The Winter Soldier, as Bucky was starting to remember the accident that lead to his capture by HYDRA, as well as Dr. Arnim Zola’s implantation of Barnes’ juiced up metal prosthetic arm. It’s this longing that needs to be crushed, and by the end of the process, that’s exactly what happens.
Rusted"Rusted" means absolutely nothing, unless we’re thinking about Bucky’s bi-monthly maintenance regimen which keeps his arm nice and strong. However, going by the first command word, this could be a further symbolic gesture that signifies a sort of corruptive countdown that puts Bucky out of commission, and awakens the Winter Soldier within. Also, "rusted" is exactly the sort of adjective that Col. Helmut Zemo would use for the empire that he’s trying to topple, but considering these commands predate Zemo’s vengeance, this is merely an example of kismet.
Seventeen"Seventeen" is a nice little double edged sword, as it looks ahead to the year of release for a certain Marvel movie that’s mentioned later on in the list, but it also has a deeper connection to Bucky Barnes’ past. Depending on what source you’re going by, 1917 is the year that Bucky was born – which could also be tied into the exchange between Bucky and Steve before they walk into the Siberian stronghold. Both men acknowledge that, technically, they’re 100 years old – though in both of their cases, it’s more of an approximation, as Bucky was born in 1917, and Steve was born in 1918 according to Captain America: The Winter Soldier.
DaybreakThis trigger word doesn’t really have a huge significance to Bucky, but it does seem to speak to the events of Captain America: Civil War, both in and outside of its cinematic universe. Symbolically, a new day is dawning with the Sokovia Accords policing the activities of Avengers and other super-powered heroes, so this fits in that respect. However, when you take into account that this film is the first one in Phase 3’s line-up, one could say that daybreak has also come for the latest round of Marvel Cinematic Universe films, with this new phase getting off to a roaring start.
FurnaceFurnaces tend to be thought of as warm, even fiery objects – which would come in handy with a person who’s being dethawed from deep cryo-sleep. While Bucky is being activated during the Siberian prologue in Captain America: Civil War, he’s still warming up to the world around him, which could mean that "furnace" is included as a command to encourage the "warming up" phase of Bucky’s awakening.