desuetude

noun3

1. •
   (formal) The state when something (for example, a custom or a law) is no longer observed nor practised; disuse, obsolescence.

   • And they being in a capacity to forget by reason of desuetude, it will be a nevv pleasure to them to recall to minde their almost obliterate speculations. — 1659
2. •
   (formal) An instance of this.

   • Owing, I will believe, to Fred's sudden flurry in the unprovided moment,—unprovided, by reason of prior desuetudes and discouragements to speech, on Papa's side. — 1858
3. •
   (formal, no longer used) Chiefly followed by from or of: a cessation of practising or using something.