Born in Manderfeld, Tofahrn grew up in Germany, France, Belgium and Italy, as his father moved to find work.
Because he was fluent in both French and German languages, he was able to play a leading role in the transfer of railways in the Eupen-Malmedy region to Belgium.
His language skills saw him working closely with Ernest Bevin, but in 1931 he moved to Zürich to take a research post with the International Federation of Food and Drink Workers.
In 1943, he was appointed as Assistant General Secretary of the ITF, remaining in post under Jaap Oldenbroek and then Omer Becu, despite frequent disagreements with both.
As leader, he focused on liaising with the International Labour Organization, and encouraging the growth of trade unions in Africa, Asia and Latin America.