PIE base ‘bottom, base’.
Other possible derivatives include profundity, found, fund, bottom, abyss, and Sanskrit budhna ‘bottom’, not related to *bheudh-, as PIE base of buddha ‘awakened one’, even though to be fully awakened it is necessary to plunge to the bottom of the Ocean of Consciousness.
[Pokorny bhudh-m(e)n ‘base, ground, bottom, fundament’, p. 174.]