A compound appearing in Definitive Linguistic Notes (DLN) from 1959 glossed “without count” as a combination of pen “without” and nod- “count”. In this note Tolkien said pen- when used in this way was “referring principally to (complete) impossibility”, so pennod means “✱impossible to count”.
Sindarin
pen-nod
adjective. without count
pennod
adjective. without count, *impossible to count
adj. without count.