Narrow beds stacked vertically to save space, or to skip school or work without permission.
The 'bed' meaning comes from Scandinavian 'bunke' meaning 'a heap.' The 'skip' or 'avoid' meaning arose as slang in the 1800s, possibly from the idea of going to your bunk instead of your duties.
The phrase 'bunk bed' became wildly popular during the space-race era of the 1960s when families wanted to fit more into smaller homes—this architectural innovation shaped how kids experienced sleep and friendship across generations.
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