Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The name 'squirrel' comes from Anglo-Norman esquirel which comes from Old French escurel which stems from Latin sciurus. The native Old English word for squirrel acweorna is descended from Proto-Germanic *aikwernô which is a compound from Proto-Germanic *aiks which may be from Proto-Indo-European *h₂éyǵs. However, all possible cognates from Balto-Slavic, Albanian and Latin are of unknown origin hence it is most likely from the Funnelbeaker language but it seems that the Funnelbeaker word was borrowed from a Vasconic source (compare Basque ezkur meaning "acorn") + Proto-Indo-European *wer- meaning "squirrel". It survived into Middle English as acquerne before being replaced completely. The Old English word is of Common Germanic origin, cognates of which are still used in other Germanic languages like German Eichhörnchen, Norwegian ikorn/ekorn, Dutch eekhoorn, Swedish ekorre, and Danish egern. The squirrel family includes tree squirrels, ground squirrels, chipmunks, marmots (including woodchucks), flying squirrels, and prairie dogs amongst other rodents. Squirrels are indigenous to the Americas, Eurasia, and Africa, and were introduced by humans to Australia. The earliest known squirrels date from the Eocene period and are most closely related to the mountain beaver and to the dormouse among other living rodent families.