Why is the ninth month called September?
1520s, partial translation of Middle Dutch klapholt (borrowed into English late 14c. as clapholt), from klappen "to fit" + Low German holt "wood, board" (see holt). Cf. German Klappholz. Originally small boards of split oak, imported from northern Germany and cut by coopers to make barrel staves; the meaning "long, thin board used for roofing or to cover the exterior of wooden buildings" is from 1640s, American English.