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What is a jackboot?
A jackboot usually reaches up to just below the knee and has no zip or buttons or laces. It has to pulled on generally by using straps inside the boots. (Early jackboots, in… the period c. 1840- 1870ish or later, often extended above the knee). Those early ones looked rather like the boots worn by some 'ladies of pleasure'. :) (In World War 2 there were occasional jokes and comments about various possible sexual interpretations)..
Incidentally, the word jackboot is often used to indicate oppression, as in phrases like 'under the jackboot of ...' (MORE)