While looking something else up, I came across Merriam-Webster's new online "Time Traveler" feature today. It allows you to browse to see what words were first used in print for a particular year.
It's a lot of fun to play with but, according to Merriam-Webster, there are the factors to keep in mind when using it:
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The date may not represent the very oldest sense of the word. Many obsolete, archaic, and uncommon senses have been excluded from this dictionary, and such senses have not been taken into consideration in determining the date.
The date most often does not mark the very first time that the word was used in English. Many words were in spoken use for decades or even longer before they passed into the written language. The date is for the earliest written or printed use that the editors have been able to discover.
The date is subject to change. Many of the dates provided will undoubtedly be updated as evidence of still earlier use emerges.