Les Excentricités du langage by Lorédan Larchey (4th ed. 1862, 5th 1865, 6th 1872) is a dictionary of unusual words and unusual uses of words. Among the Gs, for example, we find “GAMBILLER : Danser” and “GIROUETTE : Homme politique dont les opinions changent selon le vent de la fortune.”. The latter remains in demand as much as ever.
The Association des Bibliophiles Universels, which has put Larchey’s work online, is hosted by the Conservatoire National des Arts et Métiers. It includes a collection of texts for which you can generate lists of frequency and lists of occurrences of a particular word. Also part of CNAM is the Conservatoire Numérique des Arts et Métiers, with a small collection of scientific texts. The emphasis seems to be on texts about electricity, but it also includes Salomon de Caus’s Raisons des forces mouvantes and Agostino Ramelli’s Diverse et artificiose machine.