Boyd’s Bible Dictionary:
(rod). Used generically for the tall grasses, sedges, flags, or rushes which grow in marshy soils. Applied to various uses by Hebrews, and source of frequent metaphor (2 Kings 18:21; Job 40:21; Isa. 19:6; Ezek. 29:6; Matt. 11:7; 12:20; 27:29).
Concise Bible Dictionary:
See WEIGHTS and MEASURES.