Meaning of 'Aathaar'
5-1-2017 | IslamWeb
Question:
Assalaamu alaykum. I was wondering; what does the Arabic word Wa Aathaaran mean? Does it mean something left behind that we can see, or just something left behind that we could or could not see? For example, the dinosaurs left fossils, but they are in the earth and we cannot see them unless we dig the up, if you know what I mean. May Allaah reward you.
Answer:
All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad 
is His slave and Messenger.
Aathaar, in the Arabic language, is the plural of Athar, which means what is left of the traces of something and of the remains of the past peoples.
Sihaah al-Jawhari reads, “Athar: what remains of the trace of something and of the effect of the sword strike. The Sunan of the Prophet are called his Aathaar.”
Ibn ‘Atiyyah said in Al-Muharrar Al-Wajeez, “The verse (which means): {…and they plowed the earth…} [Quran 30:9] [which is the translation of the Arabic: Wa Athaaru Al-Ardh] means with buildings, plowing, wars, and all the incidents which they caused to happen.”
The Quranic Encyclopedia by Ibraaheem al-Ibyaari reads:
“The Athar of something is the occurrence of what proves its existence … Allah says (what means): {Then We sent following their footsteps (Aathaarihim) Our messengers.} [Quran 57:27]; Allah also says (what means): {So observe the effects (Aathaar) of the mercy of Allah.} [Quran 30:50] Hence, the evidence of those who passed by is called Aathaar (tracks). Allah says (what means): {So they hastened [to follow] in their footsteps (Aathaarihim).} [Quran 37:70] Allah further says (what means): {He said: They are close upon my tracks (Athary).} [Quran 20:84]”
This is the meaning of the word Aathaar in the Arabic language. So it means: the existence or occurrence of an effect that proves that there is someone or something that caused it, or leaving behind something that can be seen, but what cannot be seen is not called Athar. So the example that you gave is not called Athar unless there is something that really proves it.
Allah knows best.