Or HaChaim on Genesis 47:25/אור החיים על בראשית מ״ז:כ״ה

1 והיינו עבדים לפרעה, "and we shall remain slaves to Pharaoh." They were careful to describe themselves as Pharaoh's slaves, not as Joseph's.

2They also referred to something I mentioned earlier, that Pharaoh had acquired them only as hired labourers, people obligated to work these particular lands. By saying: והיינו עבדים לפרעה, they offered their bodies to Pharaoh also so that Pharaoh owned them outright from then on. Perhaps this is the reason why the new Pharaoh in Exodus 1,9 described the Jewish people as the "nation, the children of Israel," meaning that he could not in good conscience describe them as his slaves as they had never lost their status as a free people.