mall (n.) 1737, "shaded walk serving as a promenade," generalized from The Mall, name of a broad, tree-lined promenade in St. James's Park, London (so called from 1670s, earlier Maill, 1640s), which was so called because it formerly was an open alley that was used to play pall-mall.

The term "mall" originally meant a pedestrian promenade with shops along it (that is, the term was used to refer to the walkway itself which was merely bordered by such shops), but in the late 1960s, it began to be used as a generic term for the large enclosed shopping centers that were becoming commonplace at the time.