She 'pledged' herself to silence. [=she promised that she would not say anything]
The chefs are 'pledged' to keep the restaurant's special recipe a secret.
We've all 'pledged' (our) loyalty/support/allegiance to the organization.
(..) - The king doth wake tonight and takes his muse Keeps wassail and a swaggering upspring reels, and as he drains his drafts of rhenish down... ...the kettledrum and trumpet thus bray out the triumph of his pledge - Is it a custom? - Aye, many it is But to my mind, though I am native here (..)2015 Hamlet