the.com/french doors

means A pair of hinged doors, usually glazed with glass panes nearly top to bottom, that open from the center to join two rooms or lead outside.

from The 'French' here follows a common English habit of tagging anything stylish, airy, or vaguely continental with that nationality — 'French' once signaled elegance and architectural fashion imported (or imagined to be imported) from France, where tall glazed doors opening onto gardens and balconies were a long-standing feature of grand houses. The exact coinage isn't precisely dated, but the term fits the broader pattern of English borrowing the word 'French' as shorthand for refinement, from French kissing to French windows, regardless of the item's true origin.