The word "whole" refers to something that is complete, not divided or broken. It signifies entirety, where all parts are included and nothing is missing. For example, if you say "the whole pie," it means the entire pie without any pieces taken out.
The word "whole" comes from the Old English word "hāl," which means "unhurt, sound, healthy." It is related to the Proto-Germanic hailaz, which means "wholesome, healthy," and the Proto-Indo-European root kailo-, which means "to be whole or uninjured."