There is a neat history of the early syntax of conditional expressions here https://github.com/e-n-f/if-then-else/blob/master/if-then-el... titled “if-then-else had to be invented”. It seems “else” originated in Algol 60 as a hasty translation from German. The CPL project started in the early 1960s when it was not yet certain that Algol-style block structure and keywords would become the common basis of most programming languages.