Question: I just realized that the directions in "UPload" and "DOWNload" seem arbitrary to me as a non-native English speaker. I took a look at a couple of dictionaries and they said that this word is a result of merging "down" and "load", which doesn't seem to explain anything. Where could those two directions come from?

Answer: 
Looking at the OED first use, "1976 [Science 7 May 518/1](http://science.sciencemag.org/content/192/4239/511) Software at any level can be developed on a host minicomputer and ‘down-loaded’ without code conversion", it appears to be talking about loading code from a host to a microprocessor. No real help there but I wonder if the author was thinking of taking reference books down in a library to copy out texts and then putting them back up on the shelves?
Download and Upload are far from arbitrary, they are entirely rational:

A **[Download](https://en.wikipedia.org/wiki/Download)** refers to data that is brought '**down**' from a network, the World Wide Web (Or Cloud) to reside on a local drive / computer.

**Upload** is data that is sent '**up**' to the World Wide Web (Or Cloud) from a local drive of computer.

The term originated as others have described from the pre-personal computer era, and is a Networking term.

In the good o'l days [1970's],all computing power was housed exclusively in remote Server or mainframe computers - it was too expensive for an individual to buy. 

Other than a local terminal directly wired to the 'glowing mass' of the mainframe, any other connections were "*Down the wire*", outside of a large company with a LAN, typically this would be the public telephone system. I remember visiting my Secondary School during the summer holidays in 1977 to play "Lunar Lander" via the dial-up telephone-cradle modem link to the local council mainframe computer.

[![1970's Cradle modem](https://i.stack.imgur.com/gDmHv.jpg)](https://i.stack.imgur.com/gDmHv.jpg)

As an aside: The game required the player to type in a numerical value, which was sent 'up' the telephone line to the mainframe, which would respond to the teleprinter with a message like:

> 
> "You are at 3,000' and descending at 50m/sec."
> 
> 
> 

The player would type another value and so on until you received the message:

> 
> "Congratulations, you have crashed!"
> 
> 
> 

Tv monitors and video displays were but a distant dream...

All local drives were "down the wire". 

Any keyboard inputs were sent "up the wire"...

See also: [Downstream](https://en.wikipedia.org/wiki/Downstream_(networking))