desuetude

The state when something (for example, a custom or a law) is no longer observed nor practised; disuse, obsolescence; (countable) an instance of this.

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.

For whatſoever is derived from the law of God cannot by men admit variety, nor ſuffer diminution, or goe into deſuetude, or be extinguiſh'd by abrogation: […]

Chiefly followed by from or of: a cessation of practising or using something.

[T]he beſt Chriſtians, and (vvitneſs David) the greateſt Proficients in Scripture-Knovvledge, have the keeneſt Stomacks to this Food of Souls; and the vigorouſeſt Piety, by a Deſuetude and Neglect of it, is ſubject to Faint and Pine avvay.

Again, ſome Countries were benè morati, well diſciplined in Learning, Arts, and Knowledge, but poſſibly by the Irruption of numerous Armies of Barbarous People, thoſe Countries were quickly over-grown with Barbariſm and deſuetude from their former Civility and Knowledge, and degenerated into the Ignorance and Barbariſm of their Conquerors; ſo that in a reaſonable Period of time much of their ancient Knowledge and Arts was forgotten, as if they never had it.