The Proto-Indo-European word *swelp-
Word *swelp-
Meaning smoulder, to burn
See also Homeric Greek: ἠέλιος ‘sun’
Synonyms *dhegʷh-, *h₁eus-, *dehau-, *ĝwelhₓ-, *h₂ehₓ-

Comments
Ltv. svelt, Lith. sveltu, Goth. swiltan, ON svalr, Eng. swelan, Gk. hēlios, Skr. svarati, Toch. slam/sleme