As noted by Tom McKay, the sons of outgoing president Trump enjoyed the nicknames "stank" and "choad" as high-schoolers. Don Jr is Stank, Eric is Choad. These revelations come courtesy of their yearbooks.
Choad's name was reported out en passant by Frank Runyeon in a longer profile.
During a school hockey game, Eric and other Hill boys were razzing their opponents, when all of a sudden the arena went silent and Eric shouted out, "No. 15 is a choad!"
It stuck. Eric's friends would teasingly but lovingly call him "choad" for the rest of his time at Hill.