A boot is the emblem of the English priest John Schorne (d. c.1315), centre of a popular cult, who was said to have trapped the Devil in his boot.
boot and saddle a cavalry signal to mount, from an alteration of French boute-selle ‘place-saddle’.
by one's own bootstraps by one's own efforts. A bootstrap was sewn into boots to help with pulling them on. The idiom has given rise to the term bootstrapping, meaning to ‘make use of existing resources to improve one's position’, hence the computer term booting.
See also a lie is halfway round the world before the truth has got its boots on at lie 1, seven-league boots.