The large sleeve of the Japanese kimono makes for an ideal place to hide or to hand-off money. Today kimonos are seldom worn by Japanese men (and almost never when transacting business), but the phrase sode no shita is still very much in use. Is has come to mean primarily some form of bribe.
A: Naze anna an ga tootta n daroo.
B: Iinchoo ga sode no shita demo moratteru n daroo. Soo demo nakya tooru hazu nai yo.
A: I wonder why that proposal passed.
B: Maybe the committee chairman was given some sort of bribe. Otherwise, it should never have passed.