The word, and where it came from
Xeriscape was coined by Denver Water in 1981, combining the Greek xeros (dry) with landscape. It describes water-efficient landscaping built on sound horticultural practice, not a specific look. Denver Water even trademarked the term early on to protect it, then released it into common use to promote the concept.
The single most important correction you will make in client conversations: xeriscape is not 'zero-scape.' The homeowner who pictures a rock field with three cacti and a dead yucca has seen bad design, not xeriscape. A well-executed xeriscape can be lush, colorful, and full of bloom and pollinators. It simply uses water deliberately instead of by default.
