Hebrew slang is predominantly Palestinian Arabic, or derivations thereof—e.g. mastulמסטול (stoned, zonked), ahabalאהבל (imbecile), dir balakדיר בּאלאכּ (God help you [if you do this]), saḥbakסחבק (close friend), fadiḥahפדיחה (embarrassing mistake, booboo), etc.
Hebrew idioms are predominantly literary and usually of biblical or Talmudic origin—e.g.:
People usually started by simply adopting the new surname informally, often followed by their original surname in parentheses, until their new surname becomes better known among the public—e.g. David Ben-Gurion (né Grin). Then after a year or two, they made it official by registering it at the Ministry of the Interior (or its equivalent during the British Mandate period). This was useful, as in some cases the user might decide to change the name to something else, or to tweak it (as happened in my own family).
It was a kind of nationalist affectation, to proclaim the ancestral, pre-Babylonian-exile, Israelite origins of the newly-independent Hasmonean state—a bit like the motto of the British Royal Family (Dieu et mon droit – ‘God and my right’) is in French, harking back to its Norman origins.
Modern Israel, by the way, does much the same: the Old Hebrew script is used on the modern sheqel coin (bottom left):
The difference is, in Hasmonean times, people knew what the Old Hebrew text said, whereas 99.9% of modern Israelis haven’t a clue: most people assume it says ‘sheqel’, but in fact, it spells Yehud, which ironically is not Hebrew, but the Persian name for its Judean province, dating back to the sixth century BCE, when Persia had just conquered the Babylonian empire, and allowed all exiled nations (the Judeans included) to return to their ancestral homes.
Before the invention of printing, the ‘look’ of a script was determined by those in charge of producing large amounts of text—the professional scribes.
When Judeans first adopted the Assyrian version of the Canaanite script as their new script, some time in the 6th centuring BCE, the characters looked like this (pardon the letter order, which is left-to-right order, instead of right-to-left):
You could—the letters are substantially the same (functionally speaking) as the modern Hebrew alphabet—but it is graphically less sophisticated than its derivatives, namely the Greek & Roman alphabets, and the Assyrian script which gave rise to the revised form of Hebrew from the Second Temple period onwards, known today as “Square Script”:
It means “Done and dusted”, i.e. “there’s nothing more to do—move on.”
It’s taken from the last two verses of Psalms 128, which describes the cherished vision of a future where the people of Israel are blessed, and all is good in the world—a kind of utopia, where we needn’t strive any more:
ה יברכך יהוה מציון: וראה בטוב ירושלים–כל ימי חייך.
ו וראה-בנים לבניך: שלום על-ישראל.
5 The Lord shall bless thee out of Zion: and thou shalt see the good of Jerusalem all the days of thy life.
6 Yea, thou shalt see thy children’s children, and peace upon Israel.
Pronunciation is undoubtedly very different today—but then the same is true for English of Chaucer’s or even Shakespeare’s time and today. (Heck, these days I’m reading Sinclair Lewis’s Babbit, and I’m having a hard time understanding the characters’ 1920s slang…).
I was about to dismiss this seemingly silly question with a flippant answer along the lines of “Yes, and Shakespeare’s writings were much better in the original German,” when it struck me that OP might be confusing “the Hebrew Torah” with the New Testament.