retronym

.
altering or adding to a prior word or term term that must be further defined in the light of later developments or technical innovation.

example: no one called “world war one” that until there was a “world war two” with which to contrast it. the going term during the 1914-1918 war and up to 1939 was “the great war.”
.
other employment of term retronym:

telephone becomes “rotary-dial phone” to distinguish it from the push-b-tton phones that became widespread in the 1970s and early 1980s (although rotary-dial phones still work if all you want to do is place a call and don’t need to access features like querying a bank account balance).

similarly, telephone also becomes “corded phone” to distinguish the traditional hard-wired telephone from those that are wireless in some way, such as cordless phones.

“regular” coffee to distinguish it from decaffeinated coffee; some people say “caffeinated” coffee but strictly speaking this is a grammatical back-formation, not a retronym, because “to caffeinate” would mean to add caffeine to traditional coffee.

note, though, that coca-cola is a “caffeinated” or “caffeine-containing” soft drink in its usual red-can form. now that there is a caffeine-free coca-cola “caffeinated” could find use as a retronym for “the real thing.”

“manual” or “standard” or “stick” transmission on a car, none of which terms was necessary before automatic transmissions on cars became widespread and -ssumed to be the norm.

and, of course, “acoustic” guitar.
describes a word re-created to differentiate the original from newer incarnations of the same. often preceded by “-n-log”, “acoustic” or “conventional”.
snail mail, -n-log watch, rotary-dial telephone, or in america, “ice hockey”.