This old English term, meaning pilgrim-worm, is used in Jeremiah 1:4 2:25 Amos 4:9, like "canker-worm" and "caterpillar," for the locust in one of another of its various species or transitions. These insects are very destructive even before they reach the winged state. See LOCUST.
Source: ATS Bible Dictionary
Palmer-worm
(Heb. gazam). The English word may denote either a caterpillar (as rendered by the LXX.), which wanders like a palmer or pilgrim, or which travels like pilgrims in bands (Joel 1:4; 2:25), the wingless locusts, or the migratory locust in its larva state.