As is the case with many English phrases, sic has been borrowed from Latin. Sic is the shortened form of ‘sic erat scriptum’, which means “thus was it written”. ‘Sic’ by itself means ‘thus.’
The word ‘sic’ is usually written in brackets and follows a copied or quoted word, phrase or passage. This is used to indicate that the copied text is copied exactly as it was written in the original text. This means that any erroneous or archaic spelling, surprising assertion, faulty reasoning, or other errors of transcription have been also copied exactly and have not been changed or updated.
The purpose of the usage of ‘sic’ is to indicate that the error that occurs in the text is not due to the current writer, and nor it is a typo, but rather it has been written on purpose to show the manner in which the original writer had intended.