[1][2][3] It continues to be seen as a foreign-origin phrase (and thus, unnaturalized, meaning not integrated as part of native vocabulary) in English and is therefore usually italicized in writing.
It is Medieval Latin[4] in origin and the Feet of fines, kept at The National Archives (United Kingdom), contains its first use in England on January 20, 1270, at Pedes Finium, 54 Hen.
The phrase has a technical meaning in mathematics where it is sometimes used to signal that a proof can be more generally applied to other certain cases after making some, presumably obvious, changes.
As glossed by Shira Scheindlin, judge for the Southern District of New York, for a 1998 case: "This Latin phrase simply means that the necessary changes in details, such as names and places, will be made but everything else will remain the same.
A passage of Marcel Proust's À la recherche du temps perdu includes "...j'ai le fils d'un de mes amis qui, mutatis mutandis, est comme vous..." ("A friend of mine has a son whose case, mutatis mutandis, is very much like yours.")