What does holy mackerel mean?

Answer 1

It's the alternative of a swear word to show surprise or something. If you say words like holy mackerel and Jees Louise you won't go to heck when you die. ;)

Answer 2

Mackerel Means

Answer 3

This is a minced oath,in which some other word is substituted for a sacred word or name -- like "Good grief!" instead of "Good God!" or "Heck" for "Hell", "Darn" for "Damn", etc.

But why this particular form??

'Holy mackerel' first appears in the early 19th century and is apparently related to the expression 'mackerel-snappers', a mock term of derision used against Catholics immigrants. This was based on their eating fish on Friday -- why mackerels? It may be influenced by the fact that mackerels are very cheap [what these immigrants could afford] and not highly regarded. But the suggestion that "mackerel" was suggested by (the archangel) Michael seems very likely.
http://www.takeourword.com/TOW180/page2.html

This would make it more like many other minced oaths which, in place of the name of God, Jesus, etc., substitute common or odd words that start the same way and may otherwise sound similar, such as "Jeepers Creepers" or "Jimminy Cricket" for "Jesus Christ".

Though it was originally derisive, there may again be the idea of silliness, viz, the notion that a fish (esp. the mackerel) is rather a silly thing to be regarded as holy.

For other odd minced oaths of the 19th and 20th centuries, including "holy moley" and "holy cow", see:
http://www.phrases.org.uk/bulletin_board/22/messages/23.html
http://www.wordwizard.com/ch_forum/topic.asp?TOPIC_ID=3735

Answer 4

It is the term used originally by a very small group of people who worshipped this fish.The mackerel is a very revered fish amongst these people and the term was used during special celebrations. However this phrase has some how worked its way into English slang.