a coined variation of you can
bet your bottom dollar, meaning you can be very certain or sure of something. Bottom in this
case means the last in one's possession and originally referred to the last or bottom of a pile of gambling
chips. Thus the
phrase means one can be so sure of something that one can
bet his/her last
chip (dollar) on something and know it won't be lost. This
phrase originated in America in the mid-nineteenth century.