Relative
late Middle English: from Old French relatif, -ive, from late Latin relativus ‘having reference or relation’ (see relate).
wiktionary
From Middle French relatif, from Late Latin relātīvus, from Latin relātus, perfect passive participle of referō(“to carry back, to ascribe”), from re-(“again”) + ferō(“to bear or carry”).
etymonline
relative (n.)
late 14c., realtif, in grammar, "a relative pronoun," from Old French relatif (13c.), from Late Latin relativus "having reference or relation," from Latin relatus, used as past participle of referre "bring back, bear back" (see refer), from re- "back, again" + lātus "borne, carried" (see oblate (n.)). The meaning "kinsman, kinswoman, person in the same family or connected by blood" is attested from 1650s.
relative (adj.)
early 15c., relatif, "having reference (to something), relating, depending upon," from Old French relatif and directly from Late Latin relativus "having reference or relation," from Latin relatus, used as past participle of referre "bring back, bear back" (see refer), from re- "back, again" + lātus "borne, carried" (see oblate (n.)).
Meaning "having mutual relationship, connected with each other" is from 1590s; that of "arising from or determined by relationship to something else" is from 1610s; that of "having or standing in a relation to something else" is from 1650s; that of "not absolute or existing by itself" is by 1704. In grammar, "referring to an antecedent," from 1520s.
