You are correct with your question, SRFI 1[0] describes the knil argument as the "seed" or fold state (the latter for a recursive implementation). A sentinel va

You are correct with your question, SRFI 1[0] describes the knil argument as the "seed" or fold state (the latter for a recursive implementation). A sentinel value usually refers to a final value. Regarding the etymology: transform + reduce = transduce [0] https://srfi.schemers.org/srfi-1/srfi-1.html#fold https://srfi.schemers.org/srfi-1/srfi-1.html#fold