axleyoudaoicibaDictYouDict[axle 词源字典]
axle: [17] The word axle emerges surprisingly late considering the antiquity of axles, but related terms had existed in the language for perhaps a thousand years. Old English had eax, which came from a hypothetical Germanic *akhsō, related to Latin axis. This survived in the compound ax-tree until the 17th century (later in Scotland); tree in this context meant ‘beam’.

But from the early 14th century the native ax-tree began to be ousted by Old Norse öxultré (or as it became in English axle-tree); the element öxull came from a prehistoric Germanic *akhsulaz, a derivative of *akhsō. Axle first appeared on its own in the last decade of the 16th century (meaning ‘axis’, a sense it has since lost), and became firmly established in the early 17th century.
[axle etymology, axle origin, 英语词源]
axle (n.)youdaoicibaDictYouDict
"pole or pin upon which a wheel revolves," Middle English axel-, from some combination of Old English eax and Old Norse öxull "axis," both from Proto-Germanic *akhsulaz (cognates: Old English eaxl, Old Saxon ahsla, Old High German ahsala, German Achsel "shoulder"), from PIE *aks- "axis" (see axis). Found only in compound axletree before 14c.