Language: Sinhala
Source: Period dictionary
Description
Kirichchiya is the Sinhalese word for a type of dagger. The term appears in the 1824 Sinhala English Dictionary by reverend Benjamin Clough (1791-1853) as; "poniard, dagger".1
Examples
This dagger is of an extremely rare type, and I have found only a few comparable examples.
One came from the Harry Charles Purvis Bell collection, a British civil servant in Ceylon, and was obtained by the Colombo National Museum in 1938 where it is retained under accession number 38-727-77. The museum records it as "Malay Kris knife" which is certainly a mistake, as the designs are very much Sinhalese.2

The kirichchiya in the Colombo National Museum accession number 38-727-77.
Another example was sold by Wallis & Wallis on March 18, 2019, lot 13.

The kirichchiya sold by Wallis & Wallis on March 18, 2019, lot 13.
At the base of the blade is engraved "1939".
And finally, one got listed here at Mandarin Mansion in March 2021:

The Sinhalese kirichchiya listed at Mandarin Mansion in 2021.
These daggers all share some common design features, being:
1. A blade with a clipped tip, the clipped part being beveled and concave.
2. A zoomorphic hilt with a pistol shaped hilt terminating in a bird-head pommel.
3. A finger guard projecting from the base of the blade on the edge side.
Use
The "finger guard" is perhaps not so much a guard as it is an aid in holding the piece. On the one I have held it is perfectly shaped to go around the index finger knuckle and provides extra security and stability, especially in the thrust. Held in reverse, the protrusions sits nicely around the little finger and prevents the hand to slide down the blade on impact.

Notes
1. Reverend Benjamin Clough; Sinhala English Dictionary. Colombo, Wesleyan Mission Press 1892. (After 1830 original).
2. Pilippu Hewa Don Hemasiri De Silva & Senarat Vikramasiṃha; Ancient Swords, Daggers, and Knives in Sri Lankan Museums. National Museum of Sri Lanka, 2007. Page 218, plate LXIX and page 307 plate LXXXXVII. Description on pages 309-310.