Conceptual history for the 21st century: Nicholas John on Sharing
"The Oxford English Dictionary teaches us that in the sixteenth century, the verb ‘to share’ meant ‘to cut into parts’ or ‘to divide’. A plowshare, therefore, which is the cutting edge of the plow, is so called because it ‘shares’, or splits, the earth. Likewise, when a child shares their chocolate bar they divide it: they break it up into shares, or parts. In this sense, the act of sharing is one of distribution and it is an active practice. Importantly, it is also a zero-sum game − when I give you some of my candy, I am left with less. "