The noun brevity is based on the Old French word brievete (accent on the last "e") the root of which is bref, or in English, brief (the adjective of brevity.)
The words brief and brevity, like their French roots, both unltimately drive from the Latin adjective brevis, "short." A well known sentence with this word is "ars longa, vita brevis" which literally translates as "art long, life short" - in other words, it takes a long time to learn an art, craft or skill, but we only have a short life in which to do it.
There is also an old saying: "brevity is the soul of wit" - in other words, you sound wittier if you don't say too much.
The words brief and brevity, like their French roots, both unltimately drive from the Latin adjective brevis, "short." A well known sentence with this word is "ars longa, vita brevis" which literally translates as "art long, life short" - in other words, it takes a long time to learn an art, craft or skill, but we only have a short life in which to do it.
There is also an old saying: "brevity is the soul of wit" - in other words, you sound wittier if you don't say too much.