ごめんなさい

How it works

ごめんなさい (I'm sorry) opens the apology, then the speaker explains what they're sorry for. To say something "became" a certain way, Japanese turns the adjective into an adverb and adds なる (become): 遅い(おそい) (late) shifts to 遅く(おそく) (late (adverb)), then なりました (became, polite). So it's literally "it became late" rather than "I am late" — the change of state is what's marked, in polite past form.