What are knickerboxes?

Answer 1

If you mean "knickerbocker" (there are variant spellings, but I've never seen "knickerboxes" before), it's a surname of Dutch origin that was at one time more or less synonymous with "person from New York City", or even more specifically a member of the New York City elite.

It's also used for a type of baggy pants ending just below the knee, most stereotypically worn by male children in the late 19th and early 20th centuries, also called "knee pants" or "knickers". The pants for (American) football and Baseball uniforms are a modified form of these, as are golfers' "plus fours".