古ふるぼけた

• 古ふるぼけた

  Standard spelling. The kanji 古 (old) plus kana ぼけた, from the verb 古ぼける.

• 古ふる惚ぼけた
  rarely-used kanji form

  Rare kanji form using 惚 (infatuated/senile).

• 古ふる呆ぼけた
  rarely-used kanji form

  Rare kanji form using 呆 (shocked/dumbfounded).

From the verb 古ぼける (furu-bokeru), a compound of 古 (furu, 'old') and ぼける (bokeru, 'to become senile/faded'). The exact derivation of ぼける is uncertain, but it conveys a sense of deterioration or loss of sharpness.