More short names fit in your fovea than long names so for the most common operations they are the easiest to read. It’s the same reason the most common words in human languages are the shortest (and programming languages are for humans to use so subject to the same pressure.
replyAlso, Back In The Old Days memory was very expensive and precious so short identifiers were important. Often labels were tightly constrained, for example being limited to six upper-case characters so they would fit in a single word.
The usual convention (which also occurs in natural languages) is that often-used words should be short, rarely used should (and can afford to be) more descriptive.
replyWhy waste time say (write) lot (long) word when few (short) word do trick?
replyMost people actually write small amounts of code in a day, saving a single character here and there typing hardly matters. Its a saving that amounts to seconds for a days work.
replyMore characters on the other hand prevents many potential types of mistakes, such as meaning one statement of target and actually entering another.
> What i dont understand is why does everything have to be so brief.
replyThe concept is to make things easier for people who are familiar with the language. Making things harder for that group is always counterproductive, because they are the only people who can do any useful work.