A compressed triple compound: Old English 'on-be-utan' (on-by-outside) — discussing a topic is circling it.
On the subject of; concerning; approximately; in the area or vicinity of.
From Old English 'onbūtan' (on the outside of, around), a compound of 'on' (on) + 'be-' (by) + 'ūtan' (outside), where 'ūtan' is the external form of 'ūt' (out), from Proto-Germanic *ūt, from PIE *ūd- (up, out). Literally 'on the outside of' — which became 'around' then 'concerning.' The path from spatial 'surrounding' to abstract 'regarding' is natural: what surrounds a topic is what concerns it. The prefix 'be-' from PIE *h₂embʰi (around) adds the sense of 'by, near.' German
'About' is three words compressed into one: Old English 'on-be-ūtan' = 'on-by-outside.' Its original meaning was purely spatial — 'on the outside of' something. The sense 'concerning' arose because discussing a topic means circling around it. And