An Etymological Dictionary of the German Language/Annotated/Bankert
Bankert, earlier Bankart, Bankhart, masculine, ‘bastard, bantling,’ from Middle High German banchart, masculine, ‘illegitimate child,’ literally ‘a child begotten upon the bench’; a compound of Bank. The second part is -hart, appearing in proper names as Gebhart, Reinhart, and is formed by assimilation to Bastard (older Bastart, also written Basthart).