I know that there is a concept of a Mashiach Ben Yosef and there is substantial discussion about whether he is an essential precursor to the Mashiach Ben David and what, exactly he will accomplish, but I can't figure out why he is a "Mashiach."
Doesn't the word "Mashiach" refer to having been anointed with shemen hamishcha, referring to kings and priests? A person who could be a mashiach would then have to be either from the Davidic line (the tribe of Judah) or the priestly line (the tribe of Levi).
Ignoring that the tribes from Yosef were among those lost in exile when the Kingdom of Israel was dispersed, so establishing anyone as a descendant (and still a knowledgeable and visible religious Jew) would be difficult, why would there be a construct which refers to someone not eligible to be anointed as "mashiach"?
Is the MB"Y just an exception, like Koresh, or does the term evolve into something which is not connected to anointing (the way Rashi reads Daniel 9:26, "the anointed one: Heb. מָשִׁיחַ. This is purely an expression of a prince and a dignitary.")?