From The Collaborative International Dictionary of English v.0.48:
pact \pact\ (p[a^]kt), n. [L. pactum, fr. paciscere to make a
bargain or contract, fr. pacere to settle, or agree upon; cf.
pangere to fasten, Gr. phgny`nai, Skr. p[=a][,c]a bond, and
E. fang: cf. F. pacte. Cf. Peace, Fadge, v.]
An agreement; a league; a compact; a covenant. --Bacon.
[1913 Webster]
The engagement and pact of society which goes by the
name of the constitution. --Burke.
[1913 Webster]