I found another fun fact of the bible when I was reading some comments in Christendom. Apparently, in Genesis 24:2, 47:29, it was customary at that time to swear by placing the hand on the other person's genitals.
Genesis 24:2 "He said to the chief servant in his household, the one in charge of all that he had, "Put your hand under my thigh." NIV
Genesis 47:29 "When the time drew near for Israel to die, he called for his son Joseph and said to him, "If I have found favor in your eyes, put your hand under my thigh and promise that you will show me kindness and faithfulness. Do not bury me in Egypt," NIV
"Sometimes, as in this case, a gesture is added to the oath. The gesture usually is symbolic of the task to be performed by the oath taker. For instance, by placing his hand inside Abraham's thigh (in the vicinity of or on the genitals), the servant ties his oath of obedience to the acquisition of a wife for Isaac and thus the perpetuation of Abraham's line." - The IVP Bible Background Commentary: OT p.55