Is it farther or further?
c.1500 (implied in extinguishable), from Latin extinguere/exstinguere "quench, wipe out, obliterate," from ex- "out" (see ex-) + stinguere "quench," from PIE *steig- "to prick, stick, pierce." Related: Extinguished; extinguishing.
extinguish ex·tin·guish (ĭk-stĭng'gwĭsh)
n. ex·tin·guished, ex·tin·guish·ing, ex·tin·guish·es
To bring about the extinction of a conditioned response.