Off the beaten track and anywhere in the Riff country his life would not be worth a flus (small copper coin).
flustra, flus′tra, n. one of the commonest genera of marine Polyzoa.
1839, flue, shortening of influenza. Spelling flu attested from 1893. For choice of middle syllable, not a common method of shortening in English, Weekley compares tec for detective, scrip for subscription.