Genuine
late 16th century (in the sense ‘natural or proper’): from Latin genuinus, from genu ‘knee’ (with reference to the Roman custom of a father acknowledging paternity of a newborn child by placing it on his knee); later associated with genus ‘birth, race, stock’.
wiktionary
From Latin genuinus(“innate, native, natural”), from gignere, from Old Latin genere(“to beget, produce”); see genus.
etymonline
genuine (adj.)
1590s, "natural, not acquired," from Latin genuinus "native, natural, innate," from root of gignere "to beget, produce" (from PIE root *gene- "give birth, beget"), perhaps influenced in form by contrasting adulterinus "spurious." [Alternative etymology is from Latin genu "knee," from a supposed ancient custom of a father acknowledging paternity of a newborn by placing it on his knee.] Meaning "really proceeding from its reputed source" is from 1660s. Related: Genuinely; genuineness.
