'phenom' originates from English, specifically as a clipped colloquial form of the word 'phenomenon', which ultimately comes from Greek 'phainomenon', where 'phain-' meant 'to appear' or 'to be seen'.

'phenom' changed from the longer word 'phenomenon' (from Greek 'phainomenon' via Latin/Medieval usage) and entered modern colloquial English in the 20th century as a shortened form used especially in sports and popular media.

Initially the root term referred to an observable event or appearance ('phenomenon'), but the clipped modern form 'phenom' shifted to mean an outstanding person (especially a young talent) and, by extension, an extraordinary thing or sensation.