Language: Iban (Sea Dayak)
Source: Anthony Richards; An Iban-English Dictionary, 1981.
Duku is the Iban or "Sea Dayak" general word for sword.
He also states: Duku apang is synonymous to parang ilang, the decorated Kayan sword.1 This refers to what most collectors today know as the mandau.
A langgai tinggang, one of several types of swords used by the Sea Dayak.
Glossary articles mandau and parang ilang.
1. Anthony Richards; An Iban-English Dictionary. Clarendon Press. Oxford. 1981. Page 15.