Often 'b' & 'p' are interchangeable, for example 'baggage' becomes 'pagas', 'lob' (to throw) becomes 'loopima'. The initial letter 's' is often dropped, for example 'skool' becomes 'kool', 'stool' becomes 'tool'.
What two letters can be replaced with each other a lot of the time in Estonian?
'b' & 'p'