From the comment and discussion, I am adding answer,
It seems that you are using some custom extension, so I would suggest you search in your app>code>local or app>code>community directory with "SWIFT" text. After searching I am sure that you will find this text in system.xml. If you find it then check if label is translatable or not (I don't have module to I can not check) If yes then you just need to update localization.csv (i.e en_US.csv) and need to add "SWIFT","BIC"