I don't have a Chumash in front of me so this is from memory. Rashi brings three peshotim for the words 'vayikreu lefonov avreich' the first peshat splits the word in two, 'av bechochmah ve'rach be'shonim' which means the Mitzriyim hailed Yosef as being young in years but senior in wisdom, second peshat, from the word to kneel 'birkayim' i.e. the Mitzriyim called before him 'I will bow down'. Thirdly, targum's peshat 'dein aba de'malkoh' the word 'avreich' is to be split in two, the Mitzriyim called in front of him 'this is the patron to the king'.
On the face of it, targum's peshat seems the most far-fetched as it resorts to Aramaic, involves adding the conjunction 'to' (the king), and it rejects the other two peshotim, why did targum choose this peshat?
The answer lies later on in the parshah, when Yosef reveals himself to his brothers he also tells his brothers the positions that he has been given. Yosef declares the following. 'Vayesimeinu le'av le'paroh, le'odon le'chol beisoh umo'sheil be'chol eretz mitzrayim.' We have here the three positions accorded to Yosef, patron to the king, master of his (Paroh's) household, and ruler of all Mitzrayim.
If we now go back to the beginning of the parshah and look for evidence that Pharoh actually appointed Yosef to these three positions we will easily find two out of the three. 'Atah tiyeh al beisi' - Yosef was appointed as head of Pharoh's household, Re'eh nosati lechah al kol eretz mitzrayim' - Yosef was appointed as a ruler over Mitzrayim, however the third position Yosef mentions to his brothers of being a patron to Pharoh is not mentioned specifically earlier on in the parshah. This is therefore the reason that targum chooses to interpert the word 'avreich' as 'dein aba de'malkoh' i.e. Pharoh did in fact appoint him as a patron to the king, hence this is the title the Mitzriyim used when referring to him.
According to the other peshatim of 'avreich' only two of the three appointments are recorded earlier in the parshah which is rather strange as one would expect either none or all the appointments would be recorded earlier but one would not expect the Torah to record two out of three.
The Rashbam on the words of the passuk 'vayikreu lefonov avreich' emphasizes the connection between this phrase and the words 'Vayesimeinu le'av le'paroh'. I believe the Rashbam in his brief way alludes to the above.
Thank you for following, anyway I hope you did.
