Quote:
Initialism originally referred to abbreviations formed from initials, without reference to pronunciation, but during the middle portion of the twentieth century, when acronyms and initialisms saw more use than ever before, the word acronym was coined for abbreviations which are pronounced as a word, like "NATO" or "AIDS". The term initialism is now typically taken to refer to abbreviations which are pronounced by sounding out the name of each constituent letter (e.g. HTML). Some have erroneously extended the term acronym in meaning to describe all abbreviations made from initial letters, regardless of pronunciation.
They also link to a huge list of acronyms, initialisms and acronym-initialism hybrids.
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1943 coinage from acro-, comb. form of Gk. akros "tip, end" (see acrid) + Eng. -onym "name" (abstracted from homonym; see name). The practice was non-existent before 20c. except in cabalistic esoterica and acrostic poetry.
The second part actually means "name".