An Etymological Dictionary of the German Language/verteidigen

by Friedrich Kluge

verteidigen, vb., ‘to defend, maintain, justify,’ from the equiv. MidHG. verteidingen, vertagedingen (usually tagedingen), wk. vb., of which the most frequent meaning is ‘to plead before a tribunal, settle and adjust by agreement.’ Allied to MidHG. tagedinc, teidinc (g), ‘a lawsuit fixed for a certain date, court-day, negotiation, assembly’ (with the meaning ‘gossip, talk,’ comp. Teiding). OHG. tagading, ‘legal summons, negotiations,’ is based on tag in the sense of ‘fixed period,’ and ding, ‘judicial proceedings,’ Comp. Du. verdedigen.