afterthought

Etymology 1

From after- + thought, probably modelled on forethought. Compare also the verb afterthink.

noun

1. A reflection after an act; a later or subsequent thought, action, or expedient.
   She packed her sandals only as an afterthought, but she was glad she did.
2. Something additional to the original plan or concept.
   This whole remodeling was an afterthought; we were only going to paint and call it good.
   For most of the past three decades, the natural world was treated almost as an afterthought by world leaders. If discussed at all, it was with platitudes about the need to save polar bears and tigers. August 30, 2019, Jonathan Watts, “Amazon fires show world heading for point of no return, says UN”, in The Guardian

verb

1. (very rare except in the past tense, possibly nonstandard) To expound as an afterthought.

Etymology 2

verb

1. simple past and past participle of afterthink