In Reply to: Holy mackerel posted by Tom Rumpf on May 21, 2010 at 15:01:
: Does anyone know the origin of "Holy mackerel"?. Thanks.
I assume you know that this is an interjection, expressing surprise or awe. The Wiktionary has this to say about the origin.
"ecorded from 1803 with uncertain origin, but possibly a euphemism for Holy Mary, with Mackerel being a nickname for Catholics because they ate the fish on Fridays. Another suggested explanation is the practice of selling mackerel on Sundays in the seventeenth century (because its quality deteriorates rapidly), so it was known as a holy fish."
It is possible that you haven't often heard "Holy Mary" said out loud. I haven't, except in the form, "Holy Mary, Mother of God."