There is a common custom in Israel (mostly in Sfardic communities) that after you shake someone's hand, you kiss your hand. Generally people kiss their thumb or first two fingers, in my experience. (For another question mentioning this custom, see Kissing the hand to catch a cold?.)
What is the source/origin of this custom?
Was it started by some rabbi? If so, who? And when?
Also, is it attested to in any writings? (i.e. reasons for doing it)