- GDR (German Democratic Republic)
- The East German state from 1949 to 1990, led by the SED (Socialist Unity Party of Germany), colloquially known as "East Germany." Its counterpart was the Federal Republic of Germany ("West Germany"). Both states emerged after the Second World War from the Allied occupation zones.
- The GDR was not a democracy in the Western sense, but a one-party dictatorship without free elections, a free press, or freedom of travel. The Stasi secret police surveilled the population on a massive scale; critics and so-called free spirits were persecuted, imprisoned, or forced out of the country. The inner-German border and the Berlin Wall were secured with watchtowers, mines, and automatic firing devices, and border soldiers were under orders to shoot people trying to flee. Leaving the country without permission, so-called "Republikflucht," was a criminal offence, and many people died attempting to escape.
- This very real danger is what gives the children's journey its true weight. An unauthorised border crossing was no small matter in the real GDR, it could have had serious consequences for them and their families. That is why Santa, Casiric, and Damaris repeatedly stress in the book how important it is that the children stay unnoticed and return home safely. Reunification in 1990 ended the division of Germany.
- Thälmann Pioneers / Young Pioneers
- State-directed upbringing in everyday GDR life rested on a tightly woven political-ideological system whose foundation was laid in primary school. From first grade, children were enrolled as Young Pioneers and wore a blue neckerchief. From fourth grade, around age ten, came promotion to Thälmann Pioneers, named after KPD chairman Ernst Thälmann. Their distinguishing mark was the characteristic red neckerchief, usually made of Dederon, a synthetic fabric typical of the GDR. Superficially similar to a scouting movement, they were firmly embedded in the SED's state indoctrination and control system. This first phase ended as planned around eighth grade, at about age fourteen.
- Ernst Thälmann
- Chairman of the Communist Party of Germany (KPD) until 1933. Arrested by the National Socialists, held in solitary confinement for eleven years, and murdered in 1944 at Buchenwald concentration camp. The GDR named its Pioneer organisation after him.
- FDJ (Free German Youth)
- The next fixed step in a socialist life course was the move from Thälmann Pioneer to the FDJ. Tom, too, has this milestone in mind in the book when he mentally trades his red Pioneer neckerchief for the distinctive blue FDJ shirt. The FDJ was the GDR's sole state-approved youth organisation for 14- to 25-year-olds; its trademark was the blue shirt bearing the black-and-yellow sun emblem. Formally voluntary, it nonetheless carried heavy systemic pressure at schools: those who refused to join were considered politically unreliable, with drastic consequences for their education and career.
- Civics ("Staatsbürgerkunde")
- A compulsory school subject from seventh grade on, a central instrument for political-ideological education in the spirit of Marxism-Leninism. Its aim was indoctrination in line with the SED and unconditional loyalty to the socialist state, with systematic distancing from the "exploitative" West. Critical questions or dissenting opinions were not tolerated.
- Workers' Party / District Chairman
- This refers to the SED (Socialist Unity Party of Germany), de facto the GDR's only ruling party. A district chairman led its organisation at county level, an influential local party post.
- People's Property ("Volkseigentum")
- Official GDR concept whereby enterprises and means of production formally belonged "to the whole people" rather than to private individuals, the subject of the discussion between Santa and Tom about capitalism and socialism in the book.
- National People's Army (NVA)
- The armed forces of the GDR. According to the author's afterword, they genuinely helped clear impassable roads during the real record winter of 1978/79.
- Ministry for State Security (Stasi)
- The Ministry for State Security acted as the GDR's secret service and secret political police, tasked with safeguarding SED power and stamping out any opposition in its infancy. Tens of thousands of full-time officers and well over a hundred thousand unofficial informants made it one of the densest surveillance apparatuses in world history. Any contact with the non-socialist world abroad was treated as potential treason.
- Amateur radio was therefore also under the strictest control. The Stasi had mobile direction-finding vehicles and listening posts to locate illegal frequencies, and would deliberately deploy jamming transmitters against unauthorised radio traffic, overlaying the signal with noise and howling tones. This very interference is why, in the book, Lena's intercepted radio message sounds heavily distorted.
- Inner German Border
- The heavily fortified border between the GDR and West Germany was the physical dividing line of the Cold War: metre-high metal mesh fences fitted with automatic firing devices, minefields, anti-vehicle ditches, and raked-sand control strips, guarded around the clock by border soldiers under orders to shoot. An unauthorised border crossing was considered high treason.
- To make a children's escape attempt believable, the author draws on the real disaster winter of 1978/79: masses of snow buried fences and ditches, froze alarm systems, and made patrol routes impassable, while the guard units were preoccupied with their own survival, a window of disorganisation that makes an otherwise unrealistic border crossing plausible.
- "Over There" / "The West"
- Colloquial GDR terms for the Federal Republic of Germany, often laden with suspicion and propaganda, of the kind conveyed to the children in the book by adults.
- Youth Welfare Office
- German child and youth welfare authority, which existed in various forms in both East and West Germany.
- Konsum
- State-run retail chain of the GDR for groceries and everyday goods, comparable to a supermarket chain.
- Malt Coffee
- A caffeine-free coffee substitute made from roasted malt. Widespread in the GDR due to a chronic shortage of real bean coffee, and a staple of the daily breakfast.