The Graphics Interchange Format (GIF) was developed in 1987 by ISP CompuServe employee Steve Wilhite who insisted at the 2013 Webby Award show that the format was always intended to be pronounced as "Jif" with a soft "G" as an attempt to play on the branding of American peanut butter brand Jif -- a gimmick that went as far as CompuServe workers saying "choosy developers choose GIF."
Nonetheless, the word is commonly enough pronounced with hard G (like the word gift) that mainstream dictionaries including American Heritage, Merriam-Webster's and the New Oxford American now have both pronunciations listed.
Even these sources disagree about the primary pronunciation though, with American Heritage for instance favoring Jif and Merriam-Webster’s favoring Gif if you listen to their audio examples. Ultimately it's been decided that both sides are correct and that the g in GIF can go either way.
Usage of GIFs was on its way to extinction, before it found a place and mainstream adoption in the modern web particularly thanks to the usage of animated memes and stickers on mobile devices and cross-platform messaging.