Gabe Goldberg avers:
Some people never use one short word when more words can take up more
space. I’ve never understood the phrase “each and every” except as an
indication that those same people don’t read what they write. Do they
think it’s more comprehensive than “all”? That it adds emphasis? That an
item might escape if the entire gaggle isn’t twice included? Beats me.
Well, in some religious terms the phrase may be used to define fractions of “the All”, god, acting as one: “Each and every soul in the All”.
Many of these repetitive redundancies stem from legalese, where the Olde English scribes, paid by the word, convinced the lawyers that each and every word had its very own unique meaning. No such things as synonyms. Hence, we get “repeats, reiterates and realleges” and “rest, residue and remainder.”
There is a slight difference in connotation. “Each” indicates the items, people, or whatever individually (i.e. they will be considered as individuals) while “every” means none will be left out, but it’s only a sliver of a difference. There are no true synonyms, but we still don’t need both words.