Hurray for Lambert ten Kate! cool Still waiting for his statue somewhere.
The term ablaut (from German ab- in the sense "down, reducing" + Laut "sound") was coined in the early 19th century by the linguist Jacob Grimm, though the phenomenon was first described a century earlier by the Dutch linguist Lambert ten Kate in his book Gemeenschap tussen de Gottische spraeke en de Nederduytsche ("Commonality between the Gothic language and Dutch", 1710).

So it's like swim swam swum _ 'He has swum', do we say that?
Or ----------ring rang rung _ 'He has rung the bell'?