Somewhere in crooked kingdom, Wylan mentions that his father used to bring him mallow tea and honey comb when he was sick with a lung infection. later, he says his mother got sick and died, of a lung infection.
its my own heartbreaking headcannon that they were sick at the same time, and Jan took advantage of wylan's disorientation to get rid of his mother. maybe he woke up one day, finally feeling better, only to be told that he had survived, but his mother hadnt.
On top of that, lung infections can cause lasting effects, and maybe he was left with some chronic effects, constantly leaving him scared of dying like his mother did. I can only imagine how terrified he would have been working in the tannery, breathing fumes that exacerbated the symptoms, remembering how his mother had died.
edit: wylan also mentions being scared of catching lung fever after nearly dying in the canal. breathing and drowning come up again and again in his story
