活気
かっき · kakki · JLPT N3 · noun
energy
🔋 活 alive + 気 spirit/energy = a lively, energetic spirit
活 (katsu) means alive or active, as in 生活 daily life. 気 (ki) is spirit or energy, as in 元気. Together: living energy. When katsu and ki join, the tsu becomes a small っ, so you get kakki.
活 — water radical 氵 + tongue 舌
Originally a phono-semantic compound: 氵 (water) suggests flowing or liveliness, while 舌 (tongue) hints at the sound. Early forms depicted gushing water, conveying the idea of being lively or alive. The meaning broadened from 'flowing water' to 'living, alive, active.'