IPA: /ɪnˈstɪl.eɪ.ʃən/
KK: /ɪnˈstɪl eɪ ʃən/
The process of gradually introducing an idea, feeling, or quality into someone's mind or character.
The teacher's instillation of confidence in her students helped them succeed.
Instillation is formed from "in-" (meaning into) and "stilla" (from Latin, meaning drop). The word refers to the act of introducing a substance drop by drop, typically in a medical or therapeutic context.
Think of something being introduced 'into' ('in-') a system 'drop by drop' ('stilla') — that's why instillation means to add something gradually.