Question

from which word the 'gravity' word is derived?

Answer 1

gravis is the word that taken for gravity

Answer 2

 It came from French, but prior to that it came from Latin and ultimately from a Proto-Indo-European word that meant “heavy.”

The English word meant (and still means) "weight, dignity, seriousness, solemnity of deportment or character, importance.”
the word was GRAVIS