terce(n = noun.time) tierce - the third canonical hour; about 9 a.m.;
is a kind of canonical hour

   See Tierce. [1913 Webster]

terce, n. Eccl.
1 the office of the canonical hour of prayer appointed for the third daytime hour (i.e. 9 a.m.).
2 this hour.

Etymology:
var. of TIERCE