In 1945 he succeeded R. W. Chambers as honorary director of the Early English Text Society and worked to extend its publishing program.
Onions' last twenty years were largely devoted to completing The Oxford Dictionary of English Etymology (1966), which treated over 38,000 words and went to press just prior to his death.
Late in life, two of the children described their father as "a strict and distant figure whose primary relationship was with the Dictionary rather than with them."
During World War I, Onions served in British naval intelligence where his knowledge of German proved a significant asset.
[1][5] Anne Onions, one of his daughters, worked for many years in the Earth Sciences department at the University of Oxford as the departmental secretary and financial administrator.