19-20th century vernacular for the vagina. A 'lum' was initially a slang word for the flue that drew smoke from an open fire up to the chimney on the rooftop. Lum as a slnag term is quite popular with women of a certain age and social background.
Ah'm goan away tae Benidorm tae getma auld lum swept by they spanish waiters!!
Lum is the name giving to a boy named Callum if he is a friend of a girl called Bingbing. His friends will start calling him Lum/Llamalashes/Calcilum and eventually, he will get stalked by the girl. He is not very popular but has fan accounts.