desuetude
Concise Oxford English Dictionary © 2008 Oxford University Press:
desuetude /dɪˈsjuːɪtjuːd, ˈdɛswɪ-/
▶noun formal a state of disuse.
– origin C17 (in the sense ‘cessation’): from Fr., from L. desuetudo, from desuet-, desuescere ‘make unaccustomed’, from de- (expressing reversal) + suescere ‘be accustomed’.
'desuetude' also found in these Oxford entries:
