undergird

verb4

1. •
   To strengthen, secure, or reinforce by passing a rope, cable, or chain around the underside of an object.
2. •
   To lend moral support to.
3. •
   (figurative) To give fundamental support; provide with a sound or secure basis; provide supportive evidence for.

   • For fiction, documentary, verse, and essay, she undergirds entertaining images and stories with profound themes of ecological responsibility and challenge to the suppression of human rights. — 2015
4. •
   To secure below or underneath.