The idiom to boot, meaning in addition or besides, has nothing to do with footwear. This sense of boot is left over from the Old English bt and Middle English bote, where the word meant an advantage or something included in a bargain, and the phrase to boot has been in common usage since the time of Old English.
For those of us who went to regular schools (in Malaysia, to boot), English boarding schools seemed (and still seem) exotic and glamorous. [The Places You Will Go]
It isn’t actually addressing a real problem, won’t solve the non-problem it’s addressed at and risks a trade war to boot. [Forbes]
And she lives in both France and New York City and is a translator and a solo zither concertist, to boot. [Between the Lines]
He was someone who had embraced the American dream; he practically had the mid-Atlantic accent to boot. [Telegraph]