IPA: //ˌʌndərˈɡɜrd//
KK: /ʌndərˈɡɜrd/
To provide support or strength to something from below.
The new policies are designed to undergird the economy during tough times.
Past: undergirded
Past Participle: undergirded
Undergird is formed from "under-" (meaning beneath) and "gird" (from Old English "gyrdan", meaning to encircle or bind). The word means to provide support or strengthen from beneath, as if encircling something to hold it up.
Think of providing support from 'beneath' ('under-') and 'binding' ('gird') something to make it stronger.