Gravitas \GRAV-uh-tahs\ , noun;
1. High seriousness (as in a person's bearing or in the treatment of a subject)
This word dates to 1924 from Latin gravitas, which is literally "weight, heaviness" but figuratively "dignity, presence, influence" in regards to people.
Latin gravitas is also the forebear of gravity, which entered the language much earlier. Gravity dates to the 1500's ("weight, dignity, seriousness") from Middle French gravité ("seriousness, thoughtfulness") which comes directly from Latin gravitatem, the nominative of gravis, which derives from gravis ("heavy").
Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Friday, April 1
Etymologies come from the Oxford English Dictionary and/or Etymonline.com