I was reading about the story of the markup languages and noticed that the term markup came from the phrase to mark up.
I'm confused about what does up mean in this context. I learned in school that the word up means all in many phrases. For examples, eat up, and drink up. I'm not sure if up means all in to mark up because what is the meaning of "all" in this context?
Mark up is a phrasal verb. English has many of these. Mark up can have a different meaning than mark, though it is related in meaning.
The second word in a phrasal verb sometimes doesn't have a lot of meaning in itself, or clear relation to the first word, and in those cases is just a signal to change the meaning of the first word.
Up appears as the second word in a lot of phrasal verbs, e.g. make up, get up, shut up, write up, etc.
You are correct that up can mean all with certain verbs (e.g. finish up). It can also function as an intensifier (e.g. clean up), or mean something like "on it's own" (e.g. clear up).
To add confusion, sometimes a two-word verb can have a separate meaning phrasally, yet still be able to be used non-phrasally. A lot of times the difference in meaning depends if the subject is a person or a non-person.
Me and my girlfriend are breaking up. (To break up = to end a relationship)
The snowball broke up in the air when I threw it. (Literal meaning of break = to disintegrate with up meaning "on it's own" or an intensifier).
I told that annoying person to shut up. (To shut up = to stop talking)
I shut up the cellar door. (Literal meaning of shut = to close with up functioning as an intensifier.)
From a computer point-of-view, which is the only time I've come across that word, it is used in HTML - HyperText Markup Language. In this particular case, Markup is another word for 'special code' or just 'code'. You place markups (codes) within a source text file and those markups tell the browser extra information about what is being taggged or "marked up". I suspect that the last example, the 'marking up' verb usage is was converted to a noun and this is why markup is used.
Apparently, this word has been used in publishing / word processing for a while:
from http://searchsoa.techtarget.com/definition/markup :
Markup refers to the sequence of characters or other symbols that you insert at certain places in a text or word processing file to indicate how the file should look when it is printed or displayed or to describe the document's logical structure.
Markup also is used to denote the amount a merchant increases the price of goods over what they were purchased. Buy at $1, sell at $3, the markup is $2. I guess you could say that text added to documents that describe meta information could be considered a markup, an increase in value or profit, for the target document.
It's colloquial in origin, as in mess up. Take it is idiom.
The connotation, I think, is that the piece of paper being marked (the manuscript which the editor is writing annotations on) has many marks, or is covered in marks, or has all the marks that it needs. If I simply "mark" a manuscript, I might only put one mark on it. If I "mark up" a manuscript, the implication is that I have put many marks all over it. Idioms of the form "< verb > up" often imply completion, or fully changing the state of the object.
(Historical context of "markup": Before computer typesetting was common, a piece of text to be printed would have marks — annotations — indicating whether a word should be set in a larger font, or italics, etc. These instructions would be added to the manuscript by an editor, and then used by the person who sets the metal type. In modern usage, a "markup language" serves the same purpose: to give the computer instructions about how to display the text.)
