2430: interest Aug 16, 2021

The original sense of the Latin word for 'interest', 'interesse', meant 'to be important'. This sense was not gotten from the Old French 'interest' though, even though this is exactly the same root, because at the point English took from French it meant 'damage; loss', and it was at this point the -t was added to the other English word. The early meaning having a share in ownership. It is not clear how this sense transferred to its current meaning of money to pay back on top of repaying a loan. The financial senses were cemented by the 16th and 17th centuries considering certain connotations, but the emotional sense was a little earlier.