Apparently this has always been an alternative to rye on the menus of old-school NY delis including Katz’s and 2nd Ave.
I think that’s just what they call French bread.
That’s what a friend who grew up in NYC said. Also that delis always had a choice of rye or club.
Deli-speak is its own thing. At Russ & Daughters, the smallest size of cream cheese is a bissel.