What word or phrase does your mother always say?
1640s, from abut + -ment. Originally any "junction;" the architectural usage is attested from 1793 (the notion is of the meeting-place of the arches of a bridge, etc.).
abutment a·but·ment (ə-bŭt'mənt)n. A natural tooth or implanted tooth substitute used to support or anchor a dental prosthesis.