When Hendrikus Johannes Holtslag was born about 1875, in Steenderen, Gelderland, Netherlands, his father, Gerhardus Johannes Holtslag, was 42 and his mother, Johanna Maria Elderink, was 32. He died on 25 January 1944, in Wehl, Gelderland, Netherlands, at the age of 70.
Some characteristic forenames: Dutch Geert, Gerrit, Hendrik, Klaas.
Dutch and North German: patronymic from the personal name Hendrik (see Henry 1). It is particularly located in the Dutch-German border area of Gelderland-Limburg and North Rhine-Westphalia.