Source: Standard literature
Patisthāna is the name given by Henry Parker word for a type of polearm that resembles the partisan of Europe.1 It is more commonly called patisthānaya. The Sinhalese word probably derived off the Portuguese word partidária.
For a more elaborate article, see: Patisthānaya
A fine antique Sinhalese patisthānaya. Sold by Mandarin Mansion in 2019.
1. H. Parker, Ancient Ceylon. Luzac & Co, London, 1909. Pages 534-538.