Merriam-Webster:
Partial translation of Dutch klaphout : klappen, to split, crack + Middle Dutch holt, board

Oxford Dictionaries:
early 16th century (denoting a piece of oak used for barrel staves or wainscot): partial translation of Low German klappholt 'barrel stave', from klappen 'to crack' + holt 'wood'

But yeah, Jackie, I think you're right.