In chapter 14 of the second part of A Tale of Two Cities, Jerry Cruncher points out to his son, young Jerry, that a funeral procession is coming along the street. Young Jerry replies, "Hooroar, father!" with a "mysterious significance" which leads his father to hit him on the ear.
The reason for young Jerry's inappropriate reaction and the elder Jerry's concern about it is soon revealed. Mr. Cruncher is a "resurrection man" or, in more direct terms, a grave robber. Though he is employed as the porter at Tellson's Bank, he has found this lucrative sideline to supplement his income.
In the eighteenth century, when the novel is set, and in the nineteenth century, when it was written, grave robberies were fairly common, as there was an increase in medical experiments along with a shortage of human cadavers on which to perform them. Some doctors would pay handsomely for the bodies of the recently deceased, meaning that, for a man like Cruncher, a funeral always signified a chance of extra income. Though Cruncher is an unsavory character, the notorious Burke and Hare went one step further in 1828 when they actually murdered sixteen people in order to sell their bodies to Dr. Robert Knox for dissection.