During my mathematics research, I've come across the mathematician Tammo tom Dieck. I have never come across the family name affix "tom", neither Wiktionary nor light googling give me anything conclusive, and it is also not listed on Wikipedia's list of family affixes. Is anyone familiar with this?
Dutch tom is clearly cognate to High German zum which is a contraction of zu dem "to the". The German preposition zu can be used both in a static sense ("at") and in a directional sense ("to"). In German nobility families, sometimes a distinction was maintained between von "from" some place and zu "at" some place, and sometimes even von und zu "from and at" some place (usually a castle or a fortified town). The zu indicates that a family was still living at the eponymous place at the time when the name was fixed.
Note: The static sense of zu is somewhat archaic in Modern High German, but still existent, e.g., in Universität zu Köln (official name of the Cologne university).