Holy Toledo! is an expression that's probably slipped out of usage now except among comic book characters and government officials with a taste for mild expletives. The phrase has a curious etymology. In medieval and Renaissance Europe, two cities were considered great centers of mystical and occult learning, Toledo being one. Its high-vibrational, otherworldly nature can be seen in the paintings of El Greco, who frequently chose the city as a subject. Depicted in his characteristically elongated style, Toledo seems to be soaring upward, aspiring to something greater than the daily affairs of mankind: buying and selling, eating and drinking, working and sleeping. http://www.worldandi.com/specialreport/2003/February/Sa22908.htm

"Holy Toledo!" is an exclamation of surprise used in American and Canadian English. It is widely believed to have stemmed from the common presence of TOLEDO Scales found throughout retail stores and sidewalk displays after the turn of the 19th Century. Shoppers and onlookers would use the expression to voice their dismay when they saw how much something (or someone) weighed. The TOLEDO Scale Corporation was the largest U.S. manufacturer of industrial and retail scales. Its founder, Henry Theobald, had launched an innovative store scale with an automatic weight and price display in 1901, and through continued innovation, TOLEDO established its leadership thereafter as a standard in the weights & measurements business. TOLEDO scales can still be commonly found in your local grocery where you use them to weigh fresh produce. They have a large dial display (like a clock face) and a hanging basket. In the past their larger companion models were commonly found as a novelty item on sidewalk displays on which you could stand on the scale, drop a coin and receive your weight stamped on a card accompanied with a token fortune, etc. Onlookers and passersby would sometimes gawk when perhaps an overweight person would use the scale and their weight was displayed on the large dial for all to see and exclaim "Holy Toledo!"

"holy Toledo! - This exclamation of surprise refers to Toledo, Spain, which became one of the great centers of Christian culture after its liberation from the Moors in 1085. Its thirteenth-century Gothic cathedral, one of the largest in Europe, is the seat of the Cardinal Archbishop of Spain." "Morris Dictionary of Word and Phrase Origins" by William and Mary Morris (HarperCollins, New York, 1977, 1988). http://www.phrases.org.uk/bulletin_board/5/messages/792.html

hey, i am gonna say that the expression holy toledo came when someone put on a lot of weight & stepped on a Toledo scale, couldn't believe the number and said "HOLY TOLEDO" instead of holy s__t. Thats what I think, we have all done it before that shocking site of the scale & the increase from the last time. lol steve...

I first heard it said by clinger in mash