lethargic (adj.)
late 14c., litargik, "morbidly drowsy, manifesting lethargy," from Latin lethargicus "affected with lethargy," from Greek lethargikos "drowsy," from lethargos "forgetful; inactive" (see lethargy). From 1590s as "pertaining to lethargy." Related: Lethargically. In 17c. also with a verb form, lethargize, and a noun, letharge "lethargic patient."