Halidom /(hăl"ĭ*dŭm)/

Hal·i·dom

Halidom

n.
  1. Holiness; sanctity; sacred oath; sacred things; sanctuary; -- used chiefly in oaths. [Archaic]
    So God me help and halidom.
    — Piers Plowman.
    By my halidom, I was fast asleep.
  2. Holy doom; the Last Day. [R.]