“Holy shiitake!”

“Holy shiitake!” (often misspelled as “Holy shittake!”) is a jocular expression of surprise or astonishment that has been printed on many T-shirts. The expression doesn’t have anything in particular to do with the shiitake mushroom itself; “shiitake” sounds like “shit,” and it’s simply another way of saying ‘Holy shit!”  “Holy shiitake (mushrooms)!” has been cited in print since at least 1982.
 
A mushroom pizza—usually, but not always, using shiitake mushrooms—has been frequently named “Holy shiitake.”
 
“Holy mackerel!” is an expression of surprise that has been cited in print since at least 1867. Similar food expressions (some also rhyme with “holy”) include “Holy cannoli!”, “Holy guacamole!”, “Holy jalapeño!” and “Holy pepperoni!”
   
 
Wikipedia: Shiitake 
The shiitake (Lentinula edodes) is an edible mushroom native to East Asia, which is cultivated and consumed in many Asian countries. It is considered a medicinal mushroom in some forms of traditional medicine.
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The mushroom’s Japanese name shiitake (kanji: 椎茸) is composed of shii, the name of the tree Castanopsis cuspidata that provides the dead logs on which it is typically cultivated, and take meaning “mushroom”. The specific epithet edodes is derived from the Latin word for “edible”.
     
21 March 1982, Seattle (WA) Times, “Log of Life? The unsinkable shiitake” by John Hinterberger, Pacific sec., pg. 4, col. 3:
But holy shiitake.
 
Google Books 
Newsweek
Volume 142
2003  
Pg. 56:
Holy shiitake! That— in short, un-scientific terms— is the reaction of researchers hunting for potential new medicines in mushrooms.
 
Google Books
Cat in a Hot Pink Pursuit:
A Midnight Louie Mystery
By Carole Nelson Douglas
New York, NY: A Forge Book
2005
Pg. 208:
Holy shiitake mushrooms! she thought.
 
Urban Dictionary
holy shiitake
Holy cow, holy crap, holy guacamole, et cetera.
A statement of mild to extreme excitement, surprise, disgust, or astonishment.
A G-rated way of saying “Holy sh—.”
Holy shiitake, it’s cold outside.
by K_Lizzle October 31, 2006
 
Twitter
Tiki
‏@tikipod
Holy shiitake! I found a phone card and 2 dollars!!! I had to hunt down the condo manager and give em to him.
2:20 PM - 31 Mar 2008
 
Twitter     
Christopher Justice
‏@MegaJustice
Holy shittake! What a day, crawling through conduit for a fiber connection for an event, secured new office space (yeah baby!), and more.
3:31 PM - 17 Oct 2008
 
Twitter
Alex Suarez // LEFTI
‏@SUAREASY
Holy shittake mushrooms, I just found my new favorite show.. “Coolio’s Rules” I think he cooks now and has a catering company or something?
7:10 PM - 28 Oct 2008
   
Google Books
Skeleton Letters
By Laura Childs
New York, NY: The Berkley Publishing Group (Penguin Books)
2011
Pg. ?:
“Holy shiitake mushrooms,” said Ava, as more cult members appeared.
 
Google Groups: MMSHonorsPeople
stalkertown!
Robert Landi
1/24/11
What the foccacia?
Holy shiitake mushrooms!
Kiss my asterisk!
Holy crapola!