I'm sure I'm not the only one who has puzzled in my family history research over certain individuals who seem to appear from nowhere: - death or marriage records for individuals for whom there appears to be no corresponding earlier census or birth records. Sometimes it may be that they were out of the country, sometimes they previously used a different given name or put the names in a different order, but more often than not it transpires that they previously used a different surname. Finding the original surname sometimes requires quite a bit of detective work, and just recently that detective work paid off in grand style! I was delighted to make a breakthrough in my CLOSE one-name study researches when I discovered that a whole batch of unidentified 20th century CLOSEs were previously known as KLOSZ.
Several KLOSZ brothers came to London in the early 19th century from Prussia, and established bakery and grocery businesses. Another branch ran a drapery business in the Midlands. Their descendants retained the surname KLOSZ until 1914, when suddenly but not unsurprisingly it became inadvisable to have a German surname. For example Hubert J KLOSZ married Louise D ELLIS under that name in Willesden in 1913, but their children, born 1915 and 1920, were registered as CLOSE, and the couple's deaths in 1945 and 1965 are also registered as CLOSE.
I'm having to do even more detective work to find the various branches of the KLOSZ family on every census, since a name which is unfamiliar to enumerators and indexers tends to be recorded and/or transcribed in many different ways: KLOSY, KLOSS, KLASZ ... Good exercise for the little grey cells!