The intent of Environmental, Social and Governance, or ESG, investing wasn't to bring "woke capitalism" to Wall Street, its early proponents say.

Rather, ESG was designed to be another useful metric to help investors assess the health and future profitability of a company. If a company is too heavily invested in coal operations, for example, it's probably not going to do well long-term in a global economy that's cracking down on the dirty fuel.

Of course, ESG investing now is much, much more than that.

What started as a half-baked idea among low-level staffers at the United Nations has grown into the green Frankenstein of Wall Street. ESG investing is now worth nearly $2.8 trillion in assets worldwide, according to one estimate.

A big reason for the explosion is that the three-letter acronym has morphed into a vague symbol with few guidelines surrounding what it means. Put another way: It's as if farmers could market vegetables as organic but without restrictions on genetic engineering.

All of this surprises ESG pioneers.

The goal of ESG investing was "to try and create a positive virus that we could plant in mainstream finance and investment to start a different conversation that these issues are real, they're material, and they affect your long-term investments," said Paul Clements-Hunt, the former head of the U.N. Environment Programme Finance Initiative, or UNEP FI, which played a crucial role in popularizing the idea.