Eugene FARINA stated that his father had told
him years ago that when "The Boot" was a young man he was a
"lover" and "ladies man" and spent so much of his time in a
telephone booth making dates with girls that the old-time
Italians referred to BOIARDO as "The Boot". According to
FARINA, the old-time Italians did not pronounce the "th"
on booth and it came out boot.

NJcapo35,

Probably because he made a lot of booty calls

I thought it was because he would kick people a lot?

LOL That was actually from an fbi file on him.