tubercle
Botanical term for a small tuber or tuber-like swelling, especially on the stem or root of a plant. Not a common everyday word.
Several small tubercles are attached to the stem of this plant.
Compound of 芋 (imo, 'potato, tuber') and 頭 (kashira, 'head'), referring to a tuber-like swelling. The exact historical derivation is uncertain.