Good guess, but no... - it's not that hard. You just have to think about how governments raise money....
Thrift = þrift = prosperity Trust = traust = help/confidence A higher level slave could be a trustee
Scot has a referendum. Skotfreo is old english or scotfree is free of tax, skot was norse for tax. The slave answer is there must have been a slave named Scot who escaped or was allowed to be free.
Well done AK - the Scandinavian for tax, skat, did indeed become scot, with the meaning being a redistributive taxation levied as a form of municipal poor relief. The origins of the term scot free have been wrongly taken to have come from either the story of an escaped slave in America named Dred Scott,or the notorious, and entirely false, reputation for meanness that Scottish people have. Over to you...