Is there a meaning in the parts of the word I do not get? Ekte = true / skap = wardrobe...?!?
as far as I know -skap is a suffix in Norwegian which can be equated to -hood or -ship in English (as in brotherhood; brorskap) and Ekte- is ultimately derived from middle high German and meaning law or marriage. So ekteskap is literally something like "legal marry-hood" - or simply: marriage
bryllup is the ceremony where you get married, ekteskap is what you have as a result of the ceremony.