We [help us; give us the books]
(slang) United States dollar.
Origin of Us
From Middle English us, from Old English Å«s (“us", dative personal pronoun), from Proto-Germanic *uns (“us"), from Proto-Indo-European *ne-, *nō-, *n-ge-, *n-sme- (“us"). Cognate with West Frisian us, ús (“us"), Low German us (“us"), Dutch ons (“us"), German uns (“us"), Danish os (“us"), Latin nōs (“we, us").
Middle English from Old English ūs nes-2 in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition
Derived from the similarity between the letter u and the Greek letter µ.