be sidan [OE]
beside [MI]
besì‚de
https://www.etymonline.com/word/beside#etymonline_v_11070
https://www.etymonline.com/word/be-#etymonline_v_8193
https://www.etymonline.com/word/side#etymonline_v_23487
https://quod.lib.umich.edu/m/middle-english-dictionary/dictionary/MED4825
https://quod.lib.umich.edu/m/middle-english-dictionary/dictionary/MED4824
https://bosworthtoller.com/049665
https://bosworthtoller.com/3028