completism

complete +‎ -ism. Originally from fanspeak, the slang of science fiction fans.

completism (uncountable)

1. A desire to obtain a complete collection of some type of thing.
   • 1944, John Bristol Speer, Fancyclopedia‎, Completist:

     A novel type of completism is Rothman's record and determination of attending every major convention held in this country.

   • 1986, Teresa Nielsen Hayden, “Over Rough Terrain”, in Making Book, published 1994, →ISBN, page 82:

     Completism is a form of lunacy not without honor.

   • 1992, Fanfare, volume 15, number 5, page 294:

     Caruso's records are such an important body of material that this is one case where "completism" is justified.

• completist

• Jeff Prucher, editor (2007), “completism”, in Brave New Words: The Oxford Dictionary of Science Fiction, Oxford, Oxfordshire, New York, N.Y.: Oxford University Press, →ISBN, page 25.
• Jesse Sheidlower, editor (2001–2024), “completism n.”, in Historical Dictionary of Science Fiction.