Today the word ludicrous (not ludacris, that's a rapper- but he did get his stage name from this word) is basically a synonym of ridiculous. But in the olden days, it got a bit more playful. As far as etymologists can tell, sometime in the early 1600s, it was borrowed in from the Latin word ludicrus, which meant "sportive"- here the jocosity from a sport slowly extended in meaning to a "fun time" to "laughter". Anyway, the nominative here is ludicrum, which, like that transition definition, meant "amusement" in general. This makes sense, because that is the transition between ludicrus and another Latin word, ludere, a verb meaning "to play". Ludere is from the Proto-Indo-European root leyd, which is theorized to mean "play" as well. It may seem ludicrous, but usage of ludicrous has been steadily decreasing over time; the word is slowly becoming archaic.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd