From a Tai language; compare Proto-Tai *luəkᴰ (“to scald”) (whence Thai ลวก (lûuak)). Compare also Cantonese 淥/渌 (luk6, “to boil; to scald”), which represents a Tai substrate.
luộc • (灟, 爥, 𤊒, 𤐠)
- (cooking) to boil
1957, Đoàn Giỏi, chapter 2, in Đất rừng phương Nam, Kim Đồng:Lão chỉ mặc độc chiếc quần đùi: da mặt, da lưng đỏ như cua luộc.- He only wore his shorts; the skin on his face and back was red as boiled crab.