one and the same
Identical, as in Gloria's grandfather had been, at one and the same time, a physician at the court and a general in the army. This expression is an emphatic form of “the same.” [Mid-1800s]
Were P And R Once The Same Letter?Do you ever stop and look at the shape of our alphabet? Each letter looks natural to us now, but all those lines and circles have unique histories. It’s easy to make assumptions that our letters make sense, that they developed in some orderly logical way, and one reasonable assumption would be that P and R are related to each other based on their form. …
Why Do “Flammable” And “Inflammable” Mean The Same Thing?English is a trickster of a language, evidenced by the fact that two words that appear to be antonyms can actually mean the exact same thing. For the most part we manage to bumble along without confusing the two, and can figure out which meaning is intended based on context (although in the case of regardless and irregardless some extra time is needed for teeth-gnashing). …
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.