Found at “Introduction to Elasticsearch query language | Elastic Blog” on 2023-05-19 09:46:28 +02:00.
Elastic introduced ESQL in November 2022.
ESQL is more than a language. It represents a significant investment in new compute capabilities within Elasticsearch. To achieve both the functional and performance requirements for ESQL, it is necessary to build an entirely new compute architecture. ESQL search, aggregation, and transformation functions are directly executed within Elasticsearch itself. Query expressions are not transpiled to QueryDSL for execution. Rather, we have built native support for ESQL functions within Elasticsearch.
However, in August 2022, IBM did an update on their documentation about ESQL (yes, the exact same acronym).
Extended Structured Query Language (ESQL) is a programming language defined by IBM® Integration Bus to define and manipulate data within a message flow.
There are more ESQLs. Doing a quick search reveals at least a handful of other variants.