कल्

• (Vedic) IPA^(key): /kɐl/
• (Classical) IPA^(key): /kɐl̪/

From Proto-Indo-European *kel- (“to drive”). Cognate with Latin celer (“fast”) whence English accelerate, and English hold.

कल् • (kal)

1. to impel, incite, urge

• Monier Williams (1899) “कल्”, in A Sanskrit–English Dictionary, […], new edition, Oxford: At the Clarendon Press, →OCLC, page 0260/1.
• William Dwight Whitney, 1885, The Roots, Verb-forms, and Primary Derivatives of the Sanskrit Language, Leipzig: Breitkopf and Härtel, page 017
• Otto Böhtlingk, Richard Schmidt (1879-1928) “कल्”, in Walter Slaje, Jürgen Hanneder, Paul Molitor, Jörg Ritter, editors, Nachtragswörterbuch des Sanskrit [Dictionary of Sanskrit with supplements] (in German), Halle-Wittenberg: Martin-Luther-Universität, published 2016
• Mayrhofer, Manfred (1956) Kurzgefasstes Etymologisches Wörterbuch des Altindischen [A Concise Etymological Sanskrit Dictionary] (in German), volume 1, Heidelberg: Carl Winter Universitätsverlag, page 179

• Pokorny, Julius (1959) chapter 548, in Indogermanisches etymologisches Wörterbuch [Indo-European Etymological Dictionary] (in German), volume 2, Bern, München: Francke Verlag, page 548
• Mallory, J. P. with Adams, D. Q. (2006) The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World (Oxford Linguistics), New York: Oxford University Press, →ISBN, page 405

Of uncertain origin.

Monier-Williams compares the root to Latin calculō (“to calculate”), while Mayrhofer makes no mention of this particular meaning and thus implicitly equates it with Etymology 1.

However, Turner separates this "sound, count" meaning from the above "impel, incite" meaning and derives the former from Dravidian; compare Tamil கல் (kal, “to learn, study”).

कल् • (kal)

1. to sound, count

• Monier Williams (1899) “कल्”, in A Sanskrit–English Dictionary, […], new edition, Oxford: At the Clarendon Press, →OCLC, page 0260/1.
• Turner, Ralph Lilley (1969–1985) “kaláyati”, in A Comparative Dictionary of the Indo-Aryan Languages, London: Oxford University Press