In tracing one's ancestry, one is sometimes working from fairly definitive documents, such as a census record or a wedding record in a town book, showing the place of birth and parents for both bride and groom. Yet there are degrees of reliability here. If Sarah Richardson and John Hoyt are the listed parents of the bride you are quickly up against which Sarah and John are these? There are a few in the area born about a generation earlier. It wasn't that long ago when surnames especially were written by sound, so various county clerks might write Moore, Moor, or Moar. This gets very crazy in Scandinavia once you get past 200 years ago. Ingeborg Jonasdotter - okay, we're looking for a guy named Jonas Something 20-40 years before that. I hit a point of enough uncertainty that I mark it (cap), as in Anna Carlsdotter (cap) b. about 1707, Sweden. It's my signal to myself, and to those reading my info who know that convention, that I have gone as far as I think I reliably can, so that even if there are hints from the site about possible mother or father, I didn't think them strong enough to keep going. 300 years before your own birth you have about 1000 ancestors, after all, and there is little point wasting energy tracking back 200 years worth of people who may not be your ancestors. (Which is, frankly, the problem right from the start anyway. We never 100% know, even with good documents. There are non-paternity events. We used to think these were a whopping 10%, and you will still see that number. But we have since found that these vary by culture, and 1-10% would be a more accurate statement.)
One might regard the tracing someone else did, usually a great boon that they have done the work for you, with sudden suspicion if they are accepting some very unlikely event. It's not impossible for a 16 y/o Puritan male to be marrying a 38 y/o female, but it's darn unlikely. It's unlikely for him to be marrying anyone at his age, except in the first two generations here. I once encountered an elegant, full tracing with lots of siblings included, which I relied on for some additions to my own tree - until I came across the assertion that a person had been born in Connecticut in 1607. It put everything else in question.
I was tracing a Scots line of my wife's and hit a supposed Dutchman. That's quite possible, but crossing into other countries always increases the chance that someone just got it plain wrong, or someone is hiding something. The other possibility was a Pole, even more unlikely. I put a cap on it.
Yet in recent reading I learned that there was not merely lots of trade between the Holland district of the Netherlands and both England and Scotland, there were mercenaries galore. They liked hiring each other, having a fair bit of mutual trust. We make much of the idea that mercenary soldiers would work for whoever paid them, but that is oversimple. You don't want to shell out money on distant unknown troops when you have people nearby who share enemies with you and perhaps you have fought with before. Sometimes mercenaries were resettled after a conflict was over, and the north of England and lowland Scotland were emptier - and apparently to the liking of the Dutch mercenaries. The Scottish surname Fleming comes from these resettled Dutchmen, as Flemish was an interchangeable term at the time.
There was a time, in fact, when almost half the words coming into English from Dutch...
Tangent I: Dutch and Low German were so closely related then (and even now, I hear) that they are used interchangeably when discussing early English. On the Continent the distinction is finer. Notice that we are seeing Lowlands, Low Countries, Netherlands, Low German in this discussion. This is not accidental. These were the maritime, market, and trading areas with the most mutual contact.
Back in line: ...came in via Scots...
Tangent II: Scots is not Scottish Gaelic, a Celtic language, but a Germanic sister-language to English, also descended from Early Middle English. It is also called Lowland Scots.You will hear it called a dialect, because of the old rule of applying mutual intelligibility to the dialect/language divide, but the trend now is to allow political and cultural considerations to be part of the distinction. Increasingly, if a people wants to call their dialect a language, everyone including the linguists goes along with it. Arguments ensue. The more common or powerful language-speakers consider everything a dialect of theirs, the beleaguered* minorities tend to insist on being seen as separate.
Back in line again: ...such as scone (unsurprising), croon, and dollar. Military words such as duffel and knapsack likely also came in from Dutch via Scots. I often have that "oh yeah" sense when learning that some English word comes from Dutch. They look like Dutch words, I just never noticed until someone pointed it out.
*Also a Dutch word.