7Up used to contain lithium citrate, a mood altering substance used to treat bipolar disorder until 1948
Theories as to the origin of the name vary but a straightforward explanation would be that the seven refers to the ingredients: carbonated water, sugar, citrus oils, citric acid, sodium citrate and lithium citrate. The Up could be a reference to the effect of lithium on mood. The founder of the original soda company that manufactured 7Up invented the name but he never told anyone the reasons why he named it so.