an [OE]
on [MI]
one [ME]
oun
https://www.etymonline.com/word/one#etymonline_v_7018
https://www.merriam-webster.com/dictionary/one#dictionary-entry-1
https://www.merriam-webster.com/dictionary/one#dictionary-entry-2
https://www.merriam-webster.com/dictionary/one#dictionary-entry-3
https://www.merriam-webster.com/dictionary/one#word-history
https://quod.lib.umich.edu/m/middle-english-dictionary/dictionary/MED30546
https://bosworthtoller.com/1609