The story
From beef + mami, from a partial calque of Hokkien 牛肉麵 /牛肉面 (gû-mah-mī, “beef noodles”). See also Hokkien 牛肉 (gû-mah).
Etymology from Wiktionary, CC BY-SA 4.0.
beef mami
Today it means: a mami soup dish of noodles and beef Full definition →