The spelling of "on on" may seem redundant at first glance, but it is actually a common phrase used in certain contexts. In IPA phonetic transcription, it would be represented as /ɑn ɑn/. The repetition of "on" is a way to emphasize the presence or continuation of something. For example, in a radio communication, a pilot might say "We are on on final approach" to indicate that they are currently on the final leg of their landing approach. The spelling may seem unusual, but it serves a practical purpose in communication.
The phrase "on on" has a specific usage in the context of hashing, which is a type of recreational running club activity. It is a rallying cry used by hashing groups during their runs. The etymology of "on on" in this particular sense can be traced back to the original hash running club, known as the Hash House Harriers (HHH).
The HHH was founded in 1938 in Kuala Lumpur, Malaysia, by a group of British colonial officers and expatriates. The club's name was inspired by the Selangor Club Annex, which they affectionately named "the Hash House". Members of the HHH would indulge in partaking of food and drinks there after their runs.
The term "on on" is said to have originated from Anglo-Indian slang, and it was used by the club to guide runners in the right direction during their trails.