"inflammation of a joint," 1540s, from medical Latin arthritis, from Greek (nosos) arthritis "(disease) of the joints," from arthritis, fem. of arthrites (adj.) "pertaining to joints" (Greek nosos is a fem. noun), from arthron "a joint" (from PIE root *ar- "to fit together"). The older noun form was arthetica (late 14c.).
kind of shrubby, aromatic herb (Salvia officinalis), esteemed formerly as a medicine, also used as a condiment, early 14c., from Old French sauge (13c.), from Latin salvia, from salvus "healthy" (from PIE root *sol- "whole, well-kept"). So called for the healing or preserving qualities attributed to it (sage was used to keep teeth clean and relieve sore gums and boiled in water to make a drink to alleviate arthritis). In English folklore, sage, like parsley, is said to grow best where the wife is dominant. The word was in late Old English as salvie, directly from Latin. Compare German Salbei, also from Latin.