Hey I found this on wikipedia. I will paste the important stuff here so you don't want to refer the page.
The original form of this proverb, now little used, was "Care killed the cat". In this instance, "care" was defined as "worry" or "sorrow."
The origin of the modern variation is unknown. The earliest known printed reference to the actual phrase "Curiosity killed the cat" is in James Allan Mair's 1873 compendium
A handbook of proverbs: English, Scottish, Irish, American, Shakesperean, and scriptural; and family mottoes, where it is listed as an Irish proverb on page 34.
In the 1902 edition of
Proverbs: Maxims and Phrases, by John Hendricks Bechtel, the phrase "Curiosity killed the cat" is the lone entry under the topic "Curiosity" on page 100.
O. Henry's 1909 short story "Schools and Schools" includes a mention that suggests knowledge of the proverb had become widespread by that time:
“
Curiosity can do more things than kill a cat; and if emotions, well recognized as feminine, are inimical to feline life, then jealousy would soon leave the whole world catless. ” The actual phrase appeared as the headline to a story in
The Washington Post on 4 March 1916 (page 6):
“
CURIOSITY KILLED THE CAT.
Four Departments of New York City Government Summoned to Rescue Feline.
From the New York World.
Curiosity, as you may recall—
On the fifth floor of the apartment house at 203 West 130th street lives Miss Mable Godfrey. When she came to the house about seven months ago she brought Blackie, a cat of several years' experience of life.
The cat seldom left the apartment. He was a hearth cat, not a fence cat, and did not dearly love to sing. In other respects he was normal and hence curious.
Last Tuesday afternoon when Miss Godfrey was out Blackie skipped into the grate fireplace in a rear room. He had done this many times before. But he had not climbed up the flue to the chimney. This he did Tuesday. Blackie there remained, perched on the top of the screen separating the apartment flue from the main chimney, crying for assistance. Miss Godfrey, returning, tried to induce her pet to come down. If you are experienced in felinity, you know that Blackie didn't come down.
On Wednesday the cat, curiosity unsatisfied, tried to climb higher—and fell to the first floor. His cries could still be heard by Miss Godfrey; who, to effect Blackie's rescue, communicated with the following departments:
1.
Police department.
2.
Fire department.
3.
Health department.
4.
Building department.
5.
Washington Heights court.
Among them they lowered a rope to Blackie. But it availed neither the cat nor them anything.
Thursday morning, just before noon, a plumber opened the rear wall back of the chimney. Blackie was taken out. His fall had injured his back. Ten minutes later Blackie died.
”