Comment by gnabgib
First hits on DDG, anonymous Google, Bing
ERD/ Entity Relationship Diagram https://www.lucidchart.com/pages/er-diagrams
ERM / Entity-Relationship Model https://en.wikipedia.org/wiki/Entity%E2%80%93relationship_mo...
(same-same, ERD is the more common acronym)
That is what I figured it would be, but you never know anymore with the amount of acronyms thrown around nowadays.