It may, possibly, have been given that name in honor of Charles Lindbergh, as claimed in a pervasive story. This Puerto Rican ice closely resembles the helado sold by sidewalk vendors in Queens, except that the "limber lady" transacts her business using a bucket, lowered from a back window. (The Daily News, where I learned of limber and that identifies the lady as Providence Lamultt, offers a brief video.)
Another difference with helado, at least here in the Bronx, is that limber is served without a stick. After rolling the cup gently between your hands, to thaw it, you can squeeze it carefully upward and eat from the top down. However, the preferred approach, described by two other patrons, is to squeeze with one hand while cupping and then flipping the limber with the other, so you can begin with the denser, more flavorful parts where juices have settled during freezing. (The same settling is apparent in helado, too.) Five or six flavors were available on my visit, including tamarind and passion fruit (50 cents each).
The limber lady's window, marked with small Puerto Rican flags, isn't near a building entrance, but the address below will get you close. If you have the same view as I did of that deli grocery, the window will be a little to your left, and one storey up.
Also shown: a blossoming tree up the hill. A passerby said that this unfamiliar tree, too, was a transplant from Puerto Rico.
East 181st St. between Valentine and Tiebout Aves., Tremont, Bronx