What's the original slang and formal meaning of "Don't have a cow"?Also how/when the term changed to its current meaning Connotaions/Denotations...

In spite of Bart Simpson's constant use of this
catch-phrase in The Simpsons TV series, it was not Bart (or his
writers) who originated it. The phrase can be traced back to the 1950s or possibly
before, and it may be of American origin. Its general meaning is to "don't get so worked
up." It possibly derived from a similar saying--"Don't have kittens" or "Don't have a
cat." A similar variation is "have a cow," as in "Dad had a cow when he saw my report
card."

Whereas The Simpsons first
began in 1987, the phrase "don't have a cow" was used in the teen movie
Sixteen Candles three years earlier. It was also used by Shaggy on
the Scooby Doo TV cartoon. According to one source, the writer
Gertrude Stein (1874-1946) used the term "to have a cow" in a sexual
sense.