bread-and-butter

Etymology
Reflecting that bread and butter are archetypally basic foodstuffs (daily necessities) in the places where the English language developed; compare daily bread, put bread on the table, earn one's bread, bread and water (as prisoners' diet or poverty diet), and know which side one's bread is buttered on.

Adjective

 * 1) Relating to basic sustenance or the requirements for everyday living.

Interjection

 * 1)  A general saying used to ward off bad luck
 * 2)  A saying specifically used to ward off bad luck when separating hands to walk either side of a tree