https://www.theguardian.com/world/2023/jan/04/iceland-language-culture-inspired-gaelic-settlers-says-author
The idea of Gaelic-speaking slave settlers in the early Icelandic colonisation is not a new one, but I don't think I have seen the linguistic arguments before.
It wouldn't surprise me if Strákur came into use as a word for servant - 'boy' in different languages is commonly used in that way, so much so that some 'boy' words seem to have started with that use and been applied to a male child later.
While looking up some examples, I was interested to see that garçon is believed to have come from a proto-German word which is also the origin of wretch.
There is another Icelandic word for 'boy' - drengur which is of Norse origin. It also has the earlier meaning of servant, so I'm only putting forward the Celtic servant link as a possible idea, not a certainty.