rod: [12] It seems likely that rod is related to English rood [OE]. In post-Anglo-Saxon times this has mainly been used for ‘cross of Christ’, and it now survives mainly in rood screen ‘altar screen’, but in the Old English period it was also used for ‘rod’. Where their Germanic ancestor, which also produced German rute ‘rod’ and Norwegian dialect rodda ‘stake’, came from is not clear. The use of rod for a unit of measurement dates from the mid 15th century. => rood[rod etymology, rod origin, 英语词源]