und [ON] + til [OE], until [OE]
untill
https://www.etymonline.com/word/until#etymonline_v_4529
https://www.etymonline.com/word/till#etymonline_v_13323
https://www.merriam-webster.com/dictionary/until#dictionary-entry-1
https://bosworthtoller.com/30488
https://old-norse.net/html/u.php#undir
https://old-norse.net/html/u.php#und2