Surname Janssonius (Janssonius 
) , all over the world, is a very rare cognomen. The surname Janssonius is habitual in Netherlands, where it is a rare surname, and South Africa, where it is a very rare surname.
| VARIANT | COUNTRY |
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| Janssonius | Netherlands, South Africa |
| jodocus janssonius born:1614|died:1655|; Janssonius, Jodocus; Janssonius, Jodocus, fl. 1642-1655 (b. 1614) |
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| roelof bennink janssonius (b. 1817) |
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| gerrit feiko janssonius NL (b. 1911) |
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| johannes janssonius Dutch scientific instrument maker |
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| johannes janssonius |
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