You might see it rendered yet ca mein, yakamein, ya ka mein, or under some similar moniker, and prepared in as many varieties as there are spellings (which I haven't exhausted here). This black-peppery version (small; $3.49) added pork and baby shrimp to the standard hardboiled egg and ramen-style noodles. St. Vincent is staffed by Chinese speakers (probably late of Vietnam, judging only by some of the groceries), but yat ka mein was absorbed into the city's black culinary vernacular long ago; on the menu board, you'll find it listed between egg drop soup and gumbo.
Note, too, another instance of a deli that will prepare a "poor boy," rather than po' boy or po-boy (click on the photo below, then on "all sizes," for a closer look).
St. Vincent Supermarket
2372 Constance St. (at 1st St.), New Orleans