þanne, þænne, þonne, þan [OE]
than [MI]
þan
https://www.etymonline.com/word/than#etymonline_v_10708
https://www.etymonline.com/word/then#etymonline_v_10728
https://www.merriam-webster.com/dictionary/than#dictionary-entry-1
https://www.merriam-webster.com/dictionary/than#dictionary-entry-2
https://quod.lib.umich.edu/m/middle-english-dictionary/dictionary/MED45021
https://bosworthtoller.com/31511