To touch by means of a mutual border, edge or end; to border on; to lie adjacent (to); to be contiguous (said of an area of land)
To lean against on one end; to end on, of a part of a building or wall.
The word abut comes from Middle English and Medieval Latin, originally meaning "to touch at one end" or "to reach." It is related to the concept of a boundary mark or the end of something.