The spelling of "oning" can be explained through the use of IPA phonetic transcription. /ɒnɪŋ/, the transcription for this word, represents the sounds that make up the word. The first sound, /ɒ/, represents the "uh" sound as heard in "pot". The second sound, /n/, represents the "n" sound. The third sound, /ɪ/, represents the "ih" sound as heard in "sit". The final sound, /ŋ/, represents the "ng" sound as heard in "sing". Therefore, "oning" is spelled as such to accurately represent its pronunciation.
I apologize, but it seems that "oning" is not a recognized word in the English language. It may either be a typo or an incorrect term. Could you please confirm the word or provide more context so that I can assist you effectively?