The textContent property is "inhertied" from the Node interface of the DOM Core specification. The text property is "inherited" from the HTML5 HTMLAnchorElement interface and is specified as "must return the same value as the textContent IDL attribute".
The two are probably retained to converge different browser behaviour, the text property for script elements is defined slightly differently.
Note that the DOM specification is a general specification for any kind of document (e.g. HTML, XML, SGML, etc.) whereas HTML5 is specifically for HTML that leverages and extends the DOM Core in many respects (some might say it's a "super set" of a few DOM specs plus HTML plus …).
Note that "inherited" does not mean "prototype inheritance", just the more general meaning of inherited.
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