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90% chance that it is simply referring to the evening, near sunset.
Although I hear 67% of statistics are made up on the spot.
I am astounded at the not so subtle change in the attitude of Adam and Eve when the Lord came to walk with them. For the first time in their existence they knew and had to deal with "fear". The "what if" question of the ages.
So glad they didn't bolt and run in their fear. They did stay but they were not honest due to fear.