Aithley comes from an English surname though the meaning behind it is unclear. I’ve seen it listed as meaning “born in a garden” but I doubt that’s an accurate meaning. I know that the last part, -ley, comes from Old English lēah meaning “clearing, meadow, woodland”, so it seems safe to assume that Aithley originated as a place name. The first part of the name is trickier. It may be derived from Irish aith-, the Irish cognate of Proto-Indo-European root word *āter- (fire) but somehow I don’t think that’s right. Another possible origin is that it comes from Old Norse eið “isthmus, strait” which comes from Proto-Germanic *aidiją from Proto-Indo-European *h₁ey- (to go), or from Old Norse eiðr “oath, swear word” from Proto-Indo-European *hoyt- (oath). However, all of that is just conjecture on my part. I think it’s more probable that the first element derives from Old English aet meaning “at, near, by, toward”, likely referring to something or someone who lived near a clearing. If it does derive from this element, than that would mean Athley, another English surname, is a variant of the name.
I’ve also seen some sites list it as meaning “king worthy” or “king maker” but like the meaning “born in a garden”, I think that’s more of a fanciful or wishful thinking.
Origin: Old English, Proto-Indo-European