The word 'tarp' is a 20th-century American English shortening of the older word 'tarpaulin'. 'Tarpaulin' itself has a more complex history, likely originating as a compound from 'tar' and 'palling', where 'pall' was an old term for a heavy cloth covering. The logic of the original term is clear: a 'tarpaulin' was a sheet of canvas or sailcloth waterproofed with tar. The clipped form 'tarp' retains the core semantic essence of its parent word—a protective, often waterproof sheet—while becoming the dominant, more efficient term in everyday usage, especially in contexts like camping and construction.

The word is a clipped form, not composed of productive morphemes in modern English. It originates from the full word 'tarpaulin'.