Aww, man. I wanted "An iceberg is a berg of ice," to be accepted. ;D But apparently, "berg" in English is short for "iceberg," so that would be like saying, "An iceberg is an iceberg of ice," which wouldn't make any sense ... ok, I think I'm rambling now ...
The English word 'iceberg' comes from the Dutch 'ijsberg'. Knowing that 'ijs' means 'ice' makes sense. No idea why the English adapted the dutch for iceberg, ice isn't that common here. 'Berg' means, by the way, if you haven't guessed already, 'mountain'.
'berg' is a less common word for 'mountain' in Norwegian as well. The word 'berg-og-dal-bane' (literally 'mountain-and-valley-track') means 'roller coaster' :)