1325-75;Middle Englishsquirel < Anglo-Frenchescuirel (Old Frenchescuireul) ≪ Vulgar Latin*scūrellus,*scūriolus, representing Latinsciurus (< Greekskíouros literally, shadow-tailed (ski(á) shadow + -ouros, adj. derivative of ourá tail); apparently so called because the tail was large enough to provide shade for the rest of the animal) with diminutive suffixes -ellus, -olus
1327, from Anglo-Fr. esquirel, O.Fr. escurel (Fr. écureuil), from V.L. *scuriolus, dim. of *scurius "squirrel," variant of L. sciurus, from Gk. skiouros "a squirrel," lit. "shadow-tailed," from skia "shadow" + oura "tail." Perhaps the original notion is "that which makes a shade with its tail." The verb meaning "to hoard up, store away" (as a aquirrel does nuts) is first recorded 1939; squirrely is from 1925. The O.E. word was acweorna, which survived into M.E. as aquerne.