'To let up' definitions:

Definition of 'To let up'

From: GCIDE
  • Let \Let\, v. i.
  • 1. To forbear. [Obs.] --Bacon. [1913 Webster]
  • 2. To be let or leased; as, the farm lets for $500 a year. See note under Let, v. t. [1913 Webster]
  • To let on, to tell; to tattle; to divulge something. [Low]
  • To let up, to become less severe; to diminish; to cease; as, when the storm lets up. [Colloq.] [1913 Webster]