i uh spend a lot of time thinking about whether various surprising software design choices are

a) intrinsic to the problem domain ("it turns out it DOES make sense!”)
b) made sense historically ("this made sense in 1992, but it didn't age well”)
c) just a typo/mistake (the "Referer" header)
d) related to budget/time constraints (“well, prototyping with shell scripts is fast!”)
e) cultural/organizational (“well, Google is the main funder for this project, and…”)
f) something else 

 @e06c1f25 c) I as a non native speaker didn't knew that was a spelling mistake!

There's a similiar thing in java: cloneable vs clonable. 

 @e06c1f25 do you have a stance on Git vs Mercurial?