https://cy.wikipedia.org/wiki/Arbennig:Am_y_Pwnc/Q1441 has a label and description in English, but they're both marked as being in Welsh (cy), either implicitly or explicitly:
<h1 id="firstHeading" class="firstHeading" lang="cy">Wanfried agreement</h1>
Every label and description (also for properties and statements thereof) should come with its lang attribute, when we fallback to a language different from the content language.
URL: https://www.w3.org/International/questions/qa-lang-why.en