I recently came across a very informative answer here within the Stack Exchange network where the author uses the word vindicative. I assumed the author had meant vindictive (I didn't know vindicative was a word). Google also thought I meant to search for vindictive when I looked up vindicative but to my surprise there are plenty of online dictionaries that list it as a word.
Initially my thought was it was just a matter of a variation in spelling similar to the differences we see between American and British English (the author is British), but then I came across this explanation on WikiDiff which states the following:
"As adjectives the difference between vindictive and vindicative is that vindictive is having a tendency to seek revenge when vengeful, while vindicative is having a tendency to vindicate."
What is the history/origin behind vindictive and vindicative and their respective meanings?