Arthritis

google

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mid 16th century: via Latin from Greek, from arthron ‘joint’. Arthritic was already used in late Middle English.

wiktionary

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From Latin, from Ancient Greek ἀρθρῖτις(arthrîtis, “joint-disease, gout”), from ἄρθρον(árthron, “a joint”).

etymonline

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arthritis (n.)

"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.).