Gikun word derived by applying Chinese-derived spelling 生気 (“vitality”), a term which decomposes into 生 (“life”) + 気 (“breath”), to native Japanese words いのち (inochi, “life”) + の (no, possessive particle) + いき (iki, “breath”).
生気 (いのちのいき)/生氣 (いのちのいき)[1](inochinoiki) → 命 (いのち)の 息 (いき) (inochi no iki), 生(せい)気(き) (seiki)