French: -ide from English -id?
Self-tutoring about French: the tutor mentions a relationship with English.
Some words seem to translate very similarly between French and English. Some examples seem to be -id words in English, such as livid, lucid, or insipid.
English to French: livid->livide; lucid->lucide; insipid->insipide.
Source:
Dubois, M-M, Keen, D.J., Shuey, B., Corbeil, J-C., Crocker, L.G. (1983). Larousse’s French-English Dictionary. Pocket Books New York.
Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.