So help me God

So help me God is a phrase often used to give an oath, and most commonly optional as part of an oath of office. It is also used in some jurisdictions as a form of oath for other forms of public duty, such as an appearance in court, service as a juror, etc.

The essence of the phrase is to emphasize that one means what one is saying or has said. It therefore implies greater care than usual in the act of the performance of one's duty, such as in testimony to the facts of the matter in a court of law.

The use of the phrase implies a greater degree of seriousness and obligation than is usually assigned to common conversation. See the discussion on oaths for more details.

In Australia the Oath of Allegiance is available in two forms, only one of which contains the phrase 'SO HELP ME GOD!.'

In Canada, the Oath of Office, Oath of Allegiance, and Oath of Members of the Privy Council may be sworn, and end in "So help me God." They may also be solemnly affirmed, and in such case the phrase is omitted.

The Constitution of Fiji, Chapter 17 requires this phrase for the oath of allegiance, and before service to the republic from the President's office or Vice-President's office, a ministerial position, or a judicial position.

In medieval France, tradition held that when the Duke of Brittany or other royalty entered the city of Rennes, they would proclaim "Et qu'ainsi Dieu me soit en aide."

In New Zealand the Oath of Allegiance is available, in English or Maori in two forms, one an oath containing the phrase 'so help me God' and the other an affirmation which does not. The Police Act 1958 and the Oaths Modernisation Bill still includes the phrase.

The Polish phrase is "Tak mi dopomóż Bóg" or "Tak mi, Boże, dopomóż." It has been used in most version of the Polish Army oaths, however other denominations use different phrases.

...
Wikipedia