With modern instrumentation, you can capture orders of magnitude more data that one could have before. This leads to databases that would appear "monstrous" by yesterday's standards. So to justify the purchase of some really cool, whacky-fast computer equipment; marketeers gave the information a tag so that corporate level people who have no idea what this is all about can understand the purchase. They called it "Big Data."
I deal with this working in a different arena, but one that is just as capable of generating ridiculously huge steaming heaps of nearly useless-- I mean "VERY VALUABLE"-- data.
Every generation has a few wide eyed dreamers with lots more vision than common sense. They tend to infest the hallways looking for people to talk to. They'll occasionally have lunch with sales and marketeering folk. Those clever marketeers then beginning to spew nonsense because they can't tell the difference between a wide eyed nit wit and someone who actually knows what will sell.
And that's how terms like "Big Data" get born.
Let me warn you up front about gathering data from the field. There are artifacts of the measurement process. These artifacts are usually caused by having many other priorities in the operational details. The people who gather data from many disparate sources on one very narrow parameter are actually gathering a great deal of noise. They're looking for patterns to reverse engineer someone's behavior when sitting down and talking to people is often more illuminating.
Is there still value in data analysis? YES, but before you go there, you REALLY need to spend time talking to the people and getting background data on what you're gathering and where. You have to have a very good idea of what you think the data should look like before you gather it.
I can not emphasize that last statement enough. If I had a dollar for every misguided study of "Big Data" that I've had to deal with, I'd be a wealthy man. Big Data analysis should be a lot like conducting a controlled experiment. If it isn't, you're just goofing around.