Desideratum \dih-sid-uh-RAY-tum\ or \dih-sid-uh-RAH-tum\ , noun;
1. Something desired or considered necessary
This word and its plural desiderata date to the 1650's and come from straight from Latin where it literally means "something for which desire is felt" from the past participle stem desiderare ("to long for, wish for; demand, expect"). The original sense of desiderare may have been "await what the stars will bring" from the phrase de sidere ("from the stars"). Sidere derives from sidus (the genitive of sideris), which means "heavenly body, star, constellation".
Unsurprisingly, the Latin word is also a forebear of the verb desire, which dates to the early 13th century and came to Middle English via Old French desirrer. The noun version came about 100 years later from Old French desir, derived from desirer. The sense of "lust" was first recorded another 200 or so years later in the mid-14th century. Modern French désirer means "to wish to do something".
Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Monday, February 7
Etymologies come from the Oxford English Dictionary and/or Etymonline.com