padrastro
/paˈdɾastɾo/ · B2 · noun · m
stepfather
👨👧 padre + astro: a 'star father' stepping in; the hangnail is a skin-strip 'step-parent'
Padrastro = padre (father) + the pejorative suffix -astro, which marks a 'step' or 'substitute' relation, as in madrastra and hijastro. The hangnail sense comes from the same idea: a bit of skin that is attached, but not truly part of the nail.