Yours, Etc.: Origins and Uses of 8 Sign-Offs
late 15c., from dis- "not" + content (v.). Related: Discontented; discontentedly; discontentment; discontentedness.
mid-15c., from dis- + content (adj.).
"state or condition of discontent," 1580s, from dis- + content (n.). Winter of our discontent is from "Richard III."