Etymology tree Proto-Indo-European *ster- Proto-Indo-European *sterh₃- Proto-Indo-European *-tós Proto-Indo-European *str̥h₃tós Proto-Italic *strātos Latin stratuslbor. English stratus Learned borrowing from Latin strātus (“spread or stretched out”). Coined by the British chemist and amateur meteorologist Luke Howard (1772–1864): see the 1803 quotation. Doublet of strath.