Not an odd question at all in my book.
Both my English mother and my Virginia born grandmother would keep their hankies in their sleeves. As a youth I was taught to keep a handkerchief in my rear pocket. A habit I kept till my late twenties when I quit as it was considered crass in the Arab world where I worked for four years. That's what kleenexes were for. I do have the urge on when dressing in p**nts to stick a handkerchief back there, but I no longer have a supply. On hot days working outside I usually put a bandanna in my rear pocket to wipe off the sweat. But after reading this thread, I may start putting it in my armpit!