i think the term is more prominent on the NLP side, via information retrieval (IR) and clustering. i first saw it in IR, and you'd see it in stanford's CS 124 or CS 224N, for example. if the parent is talking about people who are working on a system that has text-understanding component, i can understand their surprise.
Funny you mention Jaccard; I was looking up if IoU (Intersection over Union) has any other name known to ML people when I was preparing my self-driving car presentation (IoU is used in semantic segmentation), and found out it is called Jaccard index as well. To my surprise, all ML experts I know knew about IoU but nobody about Jaccard. I guess it might depend on which university you attended?