保温
ほおん · hoon · JLPT N1 · noun
heat
保 — person 亻 + 呆 (child/protect phonetic)
Originally an ideograph showing an adult carrying a child on the back, meaning to protect or shield. The right side 呆 evolved from a depiction of a swaddled infant. Over time the meaning broadened from 'protect a child' to 'preserve, guarantee, keep safe.'