"Ether" has been used as a motor starting fluid since the first automobiles, and in fact some of the earlier ones ran on "ether" rather than gasoline, prior to improved petro refining. It's possible that something like "ether-motor" was a trade name for a fuel or fuel additive that was popular, or at least commonly known, when the lyric was written(?).

The stuff used for starting and/or fuel line de-icing was (and where you find it still is) very corrosive, and will peel the paint off just about anything. It would certainly "take the smile off" a lost lover's face.

This is, of course wild-assed conjecture, as I have no evidence of that specific name, or anything similar, being significantly used or known at any time.

John