How do golf holes get their names, and how did this tradition come about

It is not really a tradition so much as a kind of quirk that some courses have. Augusta National, The Old Course at St Andrews to name the two most notable.

a hole is traditionally called such, because it is in the shape of a hole.

There are very few golf courses which have given names to the holes. St. Andrews may have been the first. In the states, Augusta National has named its holes after shrubs and flowers since the course was formerly a tree farm and nursery .