There seems to be some confusion in the comments.

The language is called JavaScript. It was temporarily called other things including LiveScript during early development. It was developed at Netscape to be the scripting language for Netscape's browser and server (yes, you read that right). It was also the basis for a proposed competitor to CSS called JavaScript Style Sheets only ever supported by Netscape 4.

The trademark to the name was held by Sun prior to its acquisition by Oracle. The existence of the trademark led to Microsoft calling their reverse engineered implementation of the language "JScript". In order to avoid fragmentation via incompatible implementations Netscape published an official language spec with ECMA, an international standards organization similar to ISO. Because the specification could not use the trademarked name this led to the name "ECMAScript" which the official specifications have used ever since.

ECMAScript 3 is also the basis for ActionScript 2 used in Flash by Macromedia/Adobe, which is not fully compatible with JavaScript. ActionScript 3 was heavily influenced by the proposed ECMAScript 4, which was eventually scrapped because it tried to do too many things at once (while also intentionally being backwars-incompatible) and none of the companies involved at that point could agree on anything. This led to the heavily downscaled ECMAScript 5 release as a compromise until 2005 when ECMAScript 6 started the current model of yearly releases by defining a multi-stage process for new language features.

The obvious question is why it was called JavaScript to begin with. Again, there are many wrong answers in the comments. The generally accepted history is that Sun and Netscape wanted to cooperate to bring Java into Netscape as the new universal language for applications. Java was already going to be available for cross-platform desktop applications (and later for embedded applications like on feature phones) and Java applets were supposed to bring it to the browser.

According to various people involved at the time, Netscape's own scripting language was considered a problem by Sun so in order to avoid competing with Java, JavaScript received its final name in order to be rebranded as a "light-weight scripting language" alongside the "serious application development language" of Java.

It's also worth mentioning that JavaScript in the browser not only consists of the ECMAScript spec but also the DOM APIs, which were originally written in a language agnostic way because there was no consensus for what the default language for accessing these APIs would be. In addition to JavaScript and JScript, Microsoft also pushed VBScript (based on Visual Basic) and there were some attempts to let Java access the DOM APIs from within the JVM.

With Java applets being mostly dead and JavaScript having survived all other browser scripting languages, DOM spec writers have recently moved to considering JavaScript as the primary implementation language and mapping their implementation agnostic pseudo-language to JavaScript language features explicitly. This should hopefully reduce the number of language quirks in future web APIs (like the various native "list" types that don't quite behave like JavaScript arrays or `document.all` being falsey).

So in short, JavaScript is called Java so not to compete with Java for "serious browser applications" in the 1990s and ECMAScript is originally a subset of Netscape's (and later Mozilla's) JavaScript although JavaScript has since shrunk and ECMAScript expanded (e.g. JS's `let` and `const` outside strict mode have been superceded by ECMAScript's more recent `let` and `const` in strict mode) to the point that both terms are used interchangeably regardless of the runtime environment.

If you're wondering why Netscape went with ECMA of all places instead of something more obvious: neither the IETF nor W3C wanted to get involved in programming language specifications at the time and the ISO process took too long but there was a way to fast-track ECMA standards to ISO standards. Remember that this all happened during the peak of the browser war between Netscape and Microsoft, so this was the only thing that mattered at the time.

If you want to learn more about the early history of JavaScript I'd suggest reading Brendan Eich's written history of it: https://dl.acm.org/doi/10.1145/3386327