köken: Borrowed from English mint, from Middle English mynte, from Old English minte, from late Proto-West Germanic *mintā (“mint”), from Latin menta. Doublet of munt.
Perhaps a (partial) calque of English mint green, from mint + grön (“green”). Mint normally refers to (a substance with) mint flavor (the plant is mynta). "Myntgrön" could be misread as "coin green" (see mynt (“coin”)), so perhaps avoided for that reason.