About: Holy cow (expression)

"Holy cow!" (and other similar terms), an exclamation of surprise used mostly in the United States, Canada, Australia, and England, is a minced oath or euphemism. The expression dates to at latest 1905. Its earliest known appearance was in a tongue-in-cheek letter to the editor: "A lover of the cow writes to this column to protest against a certain variety of Hindu oath having to do with the vain use of the name of the milk producer. There is the profane exclamations, 'holy cow!' and, 'By the stomach of the eternal cow!'" The phrase appears to have been adopted as a means to avoid using obscene or indecent language and may have been based on a general awareness of the holiness of cows in some religious traditions.