I'd never heard the word 'lox' before (British). Etymonline[0] suggests that it arrived in American English in the 20th century via Yiddish. So I guess technically the English word has only existed for <100 years :(
I have a larger vocabulary than probably 99% of people, including multiple regional and ethnic dialects, but I have never heard or seen this word in my entire life.
I suggest you add "any New York deli or bagel shop" to your 99th percentile list of multiple regional and ethnic dialects.
> lox, n. 2
> (lɒks)Pl. lox, loxes.[f. Yiddish laks, f. G. lachs salmon.]
> lox, n. 2
> A kind of smoked salmon.
> 1941: S. Longstreet Last Man around World xii. 135 “Listen, you lox-eater—until last year you thought herring was the only thing they took from the sea.”
> 1950: F. Allen Let. Oct. in G. Marx Groucho Lett. (1967) 73 “At the stage delicatessen..the lox is running good and the cream cheese is spreading easily.”
> 1961: B. Malamud New Life (1962) 121 “I'll bet lox to bagels that Gerald will get more for the department.”
> 1969: A. Glyn Dragon Variation ix. 293 “He..folded himself on to a stool at the counter, and ordered coffee and a bagel with lox.”
> 1972: Times 21 July 12/8 “Where in Paris,..can one enjoy a breakfast of beigles, lox (Yiddish for salmon) and cream cheese?”
> 1973: Daily Colonist (Victoria, B.C.) 16 Sept. 35/5 “The bagel..often is eaten with smoked salmon or lox from Nova Scotia.”