Skandapurana 5.209.53

5.209.53

atha dhanvatarirvaidyaḥ svabuddhyā pṛthivīpate ..
nāgālāne yato jātā nāgavallī bhaviṣyati .. 53 ..

Then the physician Dhanvantari, through his own discernment, O lord of the earth, [reflected]: / 'Since it grew at the tethering-post of an elephant (nāga), it shall be the nāgavallī (betel-vine). 53.