An Exchange-Traded Fund (ETF) tracking robotics companies just let the worst-kept secret in technology out of the bag: The robotics market is booming, and all signs suggest we're at the beginning of the curve.

The The Global X Robotics and Artificial Intelligence Thematic ETF (BOTZ) had $659 million in new investments in January at the start of the week.

Since launching in September 2016, BOTZ has grown to $2.4 billion in assets, with a monthly performance of 15 percent and a one-year performance of 66 percent.

Another robotics-themed ETF, ROBO, performed well in January, adding assets of $220 million.

The one-month performance of each would be respectable for any diversified equity fund, but analysts are calling BOTZ's big rake phenomenal for a thematic fund focusing on a niche technology sector.

The investor interest isn't particularly surprising given industry trends. The robotics market is poised to drive $135.4 billion in spending in 2019, up from $79 billion two years ago.

The sectors behind the growth include industrial robotics, where a relatively new class of collaborative robots has attracted medium- and even small-size businesses previously priced out of automation.

Robots used in fulfillment centers, including autonomous carts for materials handling and pick-and-place robots for sorting and packing are also helping drive growth in the post-Amazon e-commerce market.

Construction and medicine are poised to be new growth areas, and consumer robotics, long the exclusive purview of vacuum cleaners, are bound to gain steam in the next decade.

Much of the innovation is coming out of Japan, where BOTZ has placed fifty percent of its assets.