"selbst" = "self" + "Verstand" -> "der Verstand" (="mind"/"intellect") -> "verstehen" = "to understand"/"to comprehend" + "-lich" (="-(a)ble"/"-(a)bly")
So, literally it is more like "self-understandable"/"self-understandably" or "self-comprehensible"/"self-comprehensibly"
5. Backpfeifengesicht (German)
A face badly in need of a fist.
How about, "Nothing is taken for granted." I figured it had something to do with 'self' from selbst. (It's even spelled the same at the start.) verstehen = understand >>> self + understood got me close enough for government work. By the way, the constitution is old, granted, but try changing truths that are self-evident and you end up like every other civilization that is in ruins.
What is self-evident to you is exactly that: self-evident to you. Remember, the guy who wrote about those self-evident truths centuries ago found it equally self-evident that black people were inferior and that slavery was an acceptable form of labour. Truths do change, depending on their context.
Examples from everyday use:
You ask your mother if you may borrow her car for the next day. As a good german mom she'll reply: "Selbstverständlich kannst du mein Auto haben." (="of course, you can have my car.") --- A friend askes for your help with learning german vocabs. You'll say: "Selbstverständlich helfe ich dir!" (="Of course, I'll help you!")
The formal flare of "selbstverständlich": "Selbstverständlich können Sie die Reise auch vor Ort buchen!" (="Of course, you can book the trip on the spot.")
"Selbstverständlich" has a stronger meaning than "natürlich" and may expresses a certain generosity. Therefore it is often used if you want to fool around a bit. Saying "Aber selbstverständlich!!!" with a played "I-feel-offended,-how-can-you-doubt-even-for-a-second-my-willingness-to-help-you?!"- undertone sipping from your cup of tea can certainly bring that little something to a conversation. ;)
So to sum it up: "selbstverständlich" is not as common as "natürlich" but is used in the exact same contexts with the intention of making something sound more formal (with strangers) or to emphasize your generosity (in an entertaining way, with friends).
Disclaimer: That's just the use of these two words which I experienced (for nearly 30 years now). It is absolutely conceivable that they have different nuances of meaning in other corners of Germany. Maybe it's even family specific..
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.
(The Declaration of Independence of the united States of America)
The usage is admittedly less common in the 21st century, but it is still used.
You can follow this literal line of thought:
"selbst" (= "self")
- -> "der Verstand" (= "the mind"/"the intellect")
- -> "das Verstehen" (="the understanding"/"the comprehension")
"-lich" (= [very often] "-able"/"-ably")
- -> "verständlich" (= "understandable"/"comprehensible")
=> "selbstverständlich" = "self-comprehensible" [literally!]