Cognomen Trojahn (Trojahn 
) , globally, is quite a rare last name. The last name Trojahn is habitual in Switzerland, where it is quite a rare surname, Germany, where it is a rare surname, and Denmark. Not in comparison with a country's population, the name is most common in Germany, Brazil, and the United States.
| VARIANT | COUNTRY |
|---|---|
| Trojahn | Brazil, Switzerland, United States, Denmark, Germany |
| carl gottfried trojahn (b. 1795) |
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frank trojahn Danish officer, DK (b. 1963) |
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| manfred trojahn German composer, DE (b. 1949) |
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| melina maria trojahn researcher (ORCID 0000-0003-1827-458X) |
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| cássia trojahn researcher |
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| shawn trojahn researcher |
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| johann gottfried trojahn |
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| sophie trojahn German association football player, DE |
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