de rigueur (duh ree-GUHR)
adjective: required by fashion, custom, or etiquette
From French de rigueur (literally, of strictness), from Latin rigor. Ultimately from the Indo-European root streig- (to stroke or press), which also gave us strait, strike, streak, strict, stress, and strain. Earliest documented use: 1850
Usage (from Wordsmith)
“Glitz, glamour, and sleek metal are de rigueur at automobile exhibitions.”
India as Small Car Hub; The Economic Times (New Delhi, India); Jan 7, 2010.