2.1.434 Part 4 Section 18.104.22.168, themeFontLang (Theme Font Languages)
For additional notes that apply to this portion of the standard, please see the notes for lang, §22.214.171.124(a).
a. The standard states that the default values of languages of the theme fonts are specified by the cs, ea, and latin elements in the Theme part.
Word calculates the default languages of the theme fonts based on the Office install language and the system installed keyboards.