methylene (n.)

hydrocarbon radical occurring in many compounds, 1835, from French méthylène (1834), coined by Jean-Baptiste-André Dumas (1800-1884) and Eugène-Melchior Péligot (1811-1890) from Greek methy "wine" (see mead (n.1)) + hylē "wood" (which is of uncertain etymology) + Greek name-forming element -ene. So called because it was detected in wood alcohol.

"The breakdown of methylene into methyl and -ene, and the identification of the last syllable of methyl with the general suffix -yl, led to the use of meth- as a separate combining-element, as, for example, in methane, methacrylic" [Flood]. The color methylene-blue (1880) was derived from dimethylanaline.