Think there was no specific time and place where "bitcorn" was coined. It was basically just a play on words. The term was popularized after a professor from boston university (Mark Williams) predicted in 2013 that BTC would be trading at $10 a year later. He was named "professor bitcorn" by the community because of his video where he mispronounced bitcoin as bitcorn. Anyway, the term stuck. now people shorten it to the "corn"

The first OG bitcoin meme. Never sell your bitcorn!