Blockages in sewers are pretty common in cities across the globe. But how large a congealed mass of filth has to be before it gets its own name?

In 2013, after a 15 ton mass of wet wipes, condoms, sanitary products, and other trash that people shouldn’t flush down their toilets was removed from a London sewer under Kingston upon Thames, a new term was born—fatberg.

A worker cradles a fatberg in her arms in a London sewer. Photo credit: Adrian Dennis/AFP