Re: *dan-

My earlier post bombed.

Downs suggest horse country, grassy valleys with difficult
underlayment that make the valley otherwise unsuitable for
agriculture -- but 100% great for raising horses.

Denmark is a sand-dune blown from the Atlantic, and then, blown the
other way from the Baltic. As with Himmelberg.

This is not to say that 'dune' and 'Denmark' are etymologically
related.

Mark.