लग्

Of uncertain origin. Attempts to connect the root to रज् (raj, “to be red”) / रञ्ज् (rañj) are unconvincing, as are connections to लक्ष् (lakṣ, “to recognize; mark”).

लग् • (lag)

1. (cf. √ लक्ष्, लक्ष &c.) cl.1 P. (Dhātup. xix, 24) लगति (accord. to Nir. iv, 10 also लग्यति ; pf. ललाग Gr. ; aor. अलगीत् ib. ; fut. लगिता ib. ; लगिष्यति Pañcat. ; ind.p. लगित्वा, -लग्य Kāv.), to adhere, stick, cling or attach oneself to (loc.) MBh. Kāv. &c. (with हृदि and gen., ‘to penetrate to a person's heart’ Kathās.)
2. to take effect upon (loc.) Ṡiṡ.
3. to meet, come in contact, cut (as lines) Gol. Sch.
4. to follow closely, ensue or happen immediately Kathās.
5. to pass away (as time) Pañcat. : Caus. or cl.10. (Dhātup. xxxiii, 63) लागयति, ‘to taste’ or ‘to obtain’ ( आस्वादने, or आसादने). ([In Hindi this root often means ‘to begin.’])

• लग्न (lagna)
• लग्नक (lagnaka)

• Monier Williams (1899), “लग्”, in A Sanskrit–English Dictionary, […], new edition, Oxford: At the Clarendon Press, →OCLC, page 893/2.
• William Dwight Whitney, 1885, The Roots, Verb-forms, and Primary Derivatives of the Sanskrit Language, Leipzig: Breitkopf and Härtel, page 144
• Mayrhofer, Manfred (1996) Etymologisches Wörterbuch des Altindoarischen [Etymological Dictionary of Old Indo-Aryan]‎ (in German), volume 2, Heidelberg: Carl Winter Universitätsverlag, page 473
• Mayrhofer, Manfred (1976) Kurzgefasstes Etymologisches Wörterbuch des Altindischen [A Concise Etymological Sanskrit Dictionary] (in German), volume 3, Heidelberg: Carl Winter Universitätsverlag, page 84