ṭen - to sleep, to relax (Naumkin et al. 2015a:90)

Proto-MSA
*ṭnn - to go to sleep (Kogan 2015:574)

The origin is uncertain. Its striking similarity to Cha. Gyt. ṭən barä, Eža Muh. Msq. ṭənn balä ‘to be asleep’ (EDG 622) < PES *ṭnn ‘to be asleep’ may be due to chance coincidence. Cf. perhaps Arb. ṭnn ‘to die’ (Lane 1833). (Kogan 2015:574)