[azernik]

Because you got me curious enough to look this up:

It apparently originates from typewriters, when holding shift was quite physically taxing (since it literally shifted all the typeheads over to put alternate characters over the ribbon); so caps lock saved a lot of finger strain when typing acronyms or writing symbol-heavy text.

[krylon]

Thank you! It is kind of fascinating how much legacy from the typewriter era modern keyboard carry with them.