noun
chestnut in its burr
Refers to the spiky husk containing the chestnut; also used metaphorically for a prickly or unapproachable person.
秋になると、道にいがぐりが落ちている。
In autumn, chestnuts in their burrs lie on the road.
彼は見かけはいがぐりみたいだけど、中身は優しい。
He looks prickly like a chestnut burr, but inside he's kind.
栗 is the chestnut itself, while いがぐり is the whole spiky burr containing the nut.
Compound of いが (burr, prickly husk) and 栗 (chestnut). The exact origin of いが is uncertain, but it may be related to 毬 (iga, 'burr').