1) Nuclear physicist 2) Sir john cockcroft 3) Sir john douglas cockcroft 
[crater] The rim of this crater is worn and eroded from subsequent impacts. The satellite crater Cockroft N is intruding into the south-southwestern rim. There are small craters along the rim to the southeast, east, and north-northwest, and a small crater lies along the eastern inner wall. The interior floor is uneven in places, particularl...
[n] - British physicist who (with Ernest Walton in 1931) first split an atom (1897-1967)
Sir John Cockcroft noun British physicist who (with Ernest Walton in 1931) first split an atom (1897-1967)
1897–1967, English physicist: Nobel prize 1951.