Iterators and the loops of the form "forall X in A do ..." have been invented simultaneously with the appearance of the first version of the language C (i.e. around 1974), in the languages Alphard and CLU.

From Alphard and CLU, loops of this form have passed into one of the versions of the language Algol 68 (1977), and from there into the UNIX Bourne shell (1979), which inherited a few Algol 68 syntax features (because its author had worked at writing Algol 68 compilers).

Iterators and "forall" loops have begun to spread into mainstream programming languages, e.g. into C++, only a couple of decades after their invention.