Kickoff

NPR asked why “In the United States, the game played almost exclusively with hands is called football and the game played almost exclusively with feet is called soccer.” Dan Courtemanche, spokesman of the Major League Soccer, answered that “the word goes back to the late 1800s. As schools in England set up the modern rules for football that version was called Association Football. Somehow, the -ssocia part of the word turned into socca, which turned into soccer.”
A query in the Online Etymological Dictionary yields an interesting detail. The suffix –er “is used to make jocular or familiar formations from common or proper names (soccer being one),” which suggests that this “jocular suffix” was attached to the syllable soc of the word association. That the word soccer was indeed used in a jocular way indicates a quote from the Westminster Gazette (1/7/1894), referring to “the rival attractions of ‘rugger’ and ‘socker’”(OED) and using quotation marks around both words to signal irony.
“So would Major League Soccer ever join the rest of world and call the game what makes perfect sense? ‘Never say never,’ said Courtemanche” (NPR).

On a footnote: As with “the 'whisky/whiskey' conundrum,” where “consistency with the rest of the drinking world outweighs internal consistency,” international consistency here suggests a shift from one foot to the other, using the foot to kick instead of to measure.