from jemmy (n.) a pet-form and familiar equivalent of the name James, but possibly from jemmy (adj.) spruce, neat, neatly-made
+ jessamy (n.) a dandy, a fop (corruption of jessamine - climbing shrub with fragrant flowers)
Or, A Philosophical and Historical Essay on Beards
By Jacques Antoine Dulaure, Edward Drewe (translator), 1786
Chapter IV. Of Bearded Women.