雙掭燈 Give Him a Double Wick
只有那個老妖睡不穩，他兩隻手揉頭搓臉，不住的打涕噴，捏鼻子。行者道：「莫是他曉得了？與他個雙掭燈。」又拔一根毫毛，依母兒做了，拋在他臉上，鑽於鼻孔內。只有那个老妖睡不稳，他两只手揉头搓脸，不住的打涕喷，捏鼻子。行者道：「莫是他晓得了？与他个双掭灯。」又拔一根毫毛，依母儿做了，抛在他脸上，钻于鼻孔内。
逐句解 Line by line
Only that old fiend could not sleep sound. He rubbed his head and scrubbed his face with both hands, sneezing without a stop and pinching his nose.
The novel is precise about the symptoms, and they are the symptoms of something up your nose. 打涕噴 is to sneeze, and the whole picture is of a man fighting off a sleeping draught without knowing what it is.
Pilgrim said, "Can it be that he has got wind of it? Let us give him a double-trimmed lamp."
雙掭燈 is a lamp with two wicks drawn up, and the second character is a trade word — trimming a wick forward to make it burn brighter. Wukong means one insect up each nostril, and he says it as a lamplighter's joke. In 曉得, to get wind of, 得 is dé after a verb of knowing.
So he pulled another hair, made it up on the pattern of the first, threw it at his face and it bored into his nostril.
依母兒 is on the pattern of the mother — the original as a mould for the copy. It is a workshop word, and Wukong uses it the way a craftsman would talk about a second casting.
The double-wick joke is the sort of thing that dates a book precisely. Everyone reading this in the Ming knew what trimming a lamp wick looked like, and knew that two wicks meant twice the light, and would have heard the pun on doubling a dose immediately.
Wukong is enjoying himself. He has found his teacher alive, put a room to sleep, and is now making lamp jokes while dosing a leopard. The chapter has been grim for a very long stretch, and this is where it lets go.