呆気ない
あっけない · akkenai · JLPT N1 · noun
enough
呆 — mouth 口 + tree/wood 木
Originally a variant of 保 (to protect), depicting a person carrying a child. Over time the form simplified to 口 over 木 and the meaning shifted to 'dull, foolish, stunned.' Today 呆 mainly means dumbstruck or slow-witted, as in 发呆 (to space out).