underpinning

noun

1. a system of supports beneath a wall or the like.
2. Often underpinnings. a foundation or basis: to uncover the emotional underpinnings of an illness.
3. underpinnings, Informal.
   1. underwear, especially women’s underwear.
   2. the legs.

verb (used with object), un·der·pinned, un·der·pin·ning.

1. to prop up or support from below; strengthen, as by reinforcing a foundation.
2. to replace or strengthen the foundation of (a building or the like).
3. to furnish a foundation for; corroborate: The author’s conclusions are underpinned by references to experimental findings.

noun

1. a structure of masonry, concrete, etc, placed beneath a wall to provide support

verb -pins, -pinning or -pinned (tr)

1. to support from beneath, esp by a prop, while avoiding damaging or weakening the superstructureto underpin a wall
2. to give corroboration, strength, or support to

n.late 15c., “action of supporting or strengthening from beneath,” from under + present participle of pin (v.). Figurative sense of “prop, support” is recorded from 1580s. v.1520s (figurative); 1530s (literal), from under + pin (v.). Related: Underpinned; underpinning.