This word conveys the notion that an idea or reflection
expressed was not a part of one’s original train of thought or plan. It has,
according to a major dictionary online, been in our vernacular since 1655-1665. The concept of an afterthought is found in the Greek word for repentance, which
is demonstrated by turning around and demonstrating the opposite point of view
and practice. In the Bible in Matthew 11:20–21,
the original Greek word here for repentance is μετάνοια
(metanoia), which translated literally is ‘thinking
after’ or ‘afterthought.’

The earliest verifiable printing of the actual word, in
the original text hyphenated from one line to the next, is in the English
translation by George Stanhope, D.D., of the French work by Pierre Charon, Of 
Wisdom, Three Books,  1697:

“…and to all he conversed
with; nay, to stake his Reputation for the Truth of  an Opinion and yet Time and AfterThought have demonstrated the direct Contrary;
This bold confiding Man, I say, will be taught from hence to distrust such
hasty Arrogance…”

As Christians and Templars God and His work and will should
never be an afterthought. God must come first in our lives.