I asked a dutch pal, as i was intrigued.
He says, the guys who discovered the colonies, originally from the provinces of the netherlands that were known as north holland, and south holland, and when asked where they came from they said holland and it stuck with many.
They are known as dutch because people thought they were german, deutsch, as tha languages sounded so similar, but are different.
don't know about you, but that'll do for me.