Shiva Purana
शिवाभ्यां स्थापिता यस्मात्तस्मात्तं वटुकाः स्मृताः ॥ तपोभ्रष्टाश्च ये जाताः स्मृतास्तस्मात्तपोधमाः ॥ ५७॥
Because they had been established by Śiva and Śivā they are known as Vaṭukas. Those who neglect penance are known as Tapodhamas.
english translation
zivAbhyAM sthApitA yasmAttasmAttaM vaTukAH smRtAH ॥ tapobhraSTAzca ye jAtAH smRtAstasmAttapodhamAH ॥ 57॥
hk transliteration by Sanscript