The word inauspicious comes from the prefix "in" meaning "not" or "opposite of" combined with the word auspicious.  
 The word was first recorded in the late 1500s. 

• The Latin word inauspicatus means "without auspices" or "with bad auspices". 
   
• In the 17th century, the Latin word inauspicatus was used in English as inauspicate for a short time. 
  
  The earliest known use of the adjective inauspicious is in the late 1500s. OED's earliest evidence for inauspicious is from 1599, in the writing of William Shakespeare, playwright and poet.