The Danish love affair with twenty...

I'm not sure of the origin, nor are many Danes I suspect, but I noticed that the Danes, like the French(?), have a love affair with the number twenty! It is almost forgotten these days, I suspect, but a quick list of their numbers, with the full name, makes this more evident:

The numbers, after forty, are mutiples of twenty.

20 -- tyve
30 -- tredive
40 -- fyrre
50 -- halvtreds (halvtredsindstyve) lit. half from three times twenty ('sind' means times).
60 -- tres (tresindtyve) lit. three times twenty
70 -- halvfjerds (halvfjerdsindstyve) lit. half from four times twenty
80 -- firs (firsindtyve) lit. four times twenty
90 -- halvfems (halvfemsindtyve) lit. half from five times twenty