Nouns ending in -té are usually feminine.
The suffix marks an abstract quality.
L'adolescence est souvent une période d'insécurité.
Adolescence is often a period of insecurity.
Ça vient d'un sentiment d'insécurité.
It stems from a sense of insecurity.
Ton insécurité vient de ta religion.
Your insecurity comes from your religion.
FrenchTextbook teaches rules like this, in a full beginner course.
162 lessons, 4,000+ exercises, and 6+ hours of audio.
Try the first lesson free