My word/Oh my word

This harmless colloquial exclamation expressing surprise or amazement started out as a minced oath, where ‘word’ is substituted for ‘God’. St John’s Gospel starts with the words, “In the beginning was the Word … and the Word was God.” Thus, we have 'my word' instead of 'my God'. Eric Partridge's Dictionary of Historical Slang maintains that ‘my word’ dates from the mid-19th century, but it is surely much older than that, as indicated by Merriam-Webster, which gives a first citation from 1722. Perhaps it is even older than that, from at least the 17th century, when strong Puritan influence spawned a whole host of such minced oaths in an effort to prevent people from using God or Christ's name in vain.