
That's because it's short for 'Samboförhållande', ie. cohabitation. Living together as a couple.
sv.wikipedia.org/wiki/Sambof%C3%B6rh%C3%A5llande
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Fri 4 Jul 2014, 19:59,
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sv.wikipedia.org/wiki/Sambof%C3%B6rh%C3%A5llande