I think IBM was first with supporting refactorings for Java in Visual Age and Eclipse. Refactorings themselves emerged out of the Smalltalk community.

MS was very motivated to support that for C# as they were getting worried about losing marketshare to Java at the time and because J++ got a lot of negative press (compatibiltiy issues, vendor lockin, the usual MS stuff). In the end C# was held back by the same factors that held back J++ and it took them until very recently to openly support it on platforms other than Windows.