>> use of the linked words "off of" (where the second word is redundant) <<

Paulb I agree this seems to be of American/Canadian origin. It's one of my pet peeves, for no greater reason than that I find it ugly - after all, everyone understands it.

I've also come across it with the word 'outside', and I find it easier to guess at an origin here:

'The outside of the house is white.'
'Outside the house it is cold and miserable.' (Oh yes it is, in Sydney today )

Given that parts of speech are not taught / corrected, I can understand how many people would not distinguish 'outside' as a noun or a preposition, hence not know when 'of' is required.

Then maybe once 'outside of' is common you can extrapolate from that to 'off of'?