Hi Jens and Gav,
This is really interesting, and hard to find much information on these. From what I can find, it seems the 'ezhuthaani' term applies primarily to the stylus used to inscribe these palm leaves. Apparantly by deity in Hindu Faith this pertains to Lord Chitragupta, the younger brother of Yama, and who is a scribe and accountant in keeping accounts of the good and bad deeds of individuals. The result is determination of Heaven or hell of course as the time comes.
It would seem by the end of the 18th and into the 19th, and the surrounding presence of the British Raj, the use of the palm leaf would have been more votive than actually required, and perhaps this instrument would have been part of ceremonial use. The relatively modern concept of the folding knife had developed of course from European knives by this time and would have been well known through the increasing British colonial presence as well as trade.
The ivory notably suggests ceremony and the high quality of this very attractive piece seems to support that....the inscription....well I defer
All the best,
Jim