Although the creator of this deliberate misspelling and mispronunciation of the word “Coincidence” is not known, the first documented case of the term “Coinkydink” appears in the 1963 novel of Bernard Wolfe: “The Late Risers”, which was first published under the title “Everything Happens at Night”.
Since then, the phrase has seen limited growth in popularity, up until the 1980’s, when it started gaining traction.
“Coinkydink” would appear more and more frequently on the web in the 1990’s and early 2000’s.
It was first defined on Urban Dictionary on January 29th, 2005.
Since then, it has been used online and in real life conversations in various contexts to ease tension and to express humor.