When you hear the word “footlong” (is that one word or two?) what do you think of? If you’ve been anywhere near a TV or radio for the past several months, we’re guessing that the answer is ‘a Subway sandwich.’

What’s more, you’re probably thinking ‘$5 Footlong.’ After all, the Subway chain has poured millions of dollars into the $5 Footlong campaign featuring the catchy jingle that has been drilled into our SUB-conscious through repeated playings and various musical versions.

Now Subway is attempting to trademark the term ‘footlong’ to use exclusively for its 12-inch sub sandwiches, but the chain’s effort is being met with some resistance.

According to a report on NPR, Subway has been sending cease-and-desist letters to mom & pop restaurants, including those that have been using ‘footlong’ as part of their marketing and promotion for many years.

One prime example: Coney Island Drive Inn in Brookfield, Fla., has been selling footlong hotdogs for 40 years. The place even uses the word in its web address. Subway sent the drive-in a letter that reads: “You must immediately remove all references to FOOTLONGâ„¢ in association with sandwiches.” (That letter was quickly shared with the media and, almost as quickly, a Subway spokesman recanted it, telling NPR that they have no issue with footlong hot dogs — only sandwiches.) Subway says it has spent so much time, effort (and money) promoting the footlong concept that it has basically given the word (words?) a new meaning.

Meanwhile, lawyers have offered conflicting opinions on Subway’s ability to legally trademark such a generic term. “I’m sure Subway has spent a lot of money on their advertising campaign,’ Mark Dunn Giarratana told the Connecticut Law Tribune. ‘They don’t want other companies taking advantage of their efforts.”

On the other hand…Renee L. Mitchell, a lawyer for Blimpie, believes ‘footlong’ is too generic to trademark. ‘It would be like trademarking ‘milk.,’” Mitchell said.

The Subway chain has applied to the U.S. Patent and Trademark Office for an exclusive claim to the footlong sandwich for 12 years, likely to be renewed in perpetuity if approved. The applications were filed by the chain’s parent company, Doctor’s Associates, Inc.

The issue seems likely to end up in court. Meanwhile, expect to hear many more renditions of the $5 Footlong song, because it’s been ringing up a happy tune on Subway cash registers.