resideyoudaoicibaDictYouDict[reside 词源字典]
reside: [15] The -side of reside has no connection with English side. It comes from Latin sedēre ‘settle’ (source of English sedentary, session, etc and related to sit). Combination with the prefix re- ‘back’ produced residēre ‘settle back, remain in place, rest’, which passed into English via its present participle as resident ‘settling permanently in a place’ [14]. Reside is either a back-formation from this or a borrowing from French résider.

The past participle of residēre was residuus, whose neuter form residuum was used as a noun meaning ‘that which settles back’, hence ‘that which is left behind’. It passed into English via Old French as residue [14].
=> residue, sedentary, session, sit[reside etymology, reside origin, 英语词源]
reside (v.)youdaoicibaDictYouDict
late 15c., "to settle," from Middle French resider (15c.) and directly from Latin residere "sit down, settle; remain behind, rest, linger; be left," from re- "back, again" (see re-) + sedere "to sit" (see sedentary). Meaning "to dwell permanently" first attested 1570s. Related: Resided; residing. Also from the French word are Dutch resideren, German residiren.