Sibcy

Sibcy is a metaphor for Russia (Cold War Allegory Theory)
Sibcy could be thought of as a metaphor for Russia. His name is literally a Russian name, сибси. The entire story is an allegory of the Cold War. Apaullo represents America. It's no coincidence that the movie takes place in the winter, when it is COLD. This lends to the idea that the film is Russian propaganda, as America is portrayed as the villain, and Sibcy literally "recruits" Linnie to go against America and join his side / ideology.

Trivia

 * Sibcy shares his name with author Paul Sibcy, who he may be named after. Paul Sibcy is famous for his books centering around faith with God, which could play into the theories regarding him helping Linnie find her faith.
 * Sibcy's name is also very similar to "сибси", sharing the name with a Russian director of short films.