Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.

Category: bird 
Words: ostrich, digger, sandpiper, crane, goose
digger

Category: moral characteristic 
Words: concise, frank, matter of fact, pork, blunt
pork

Category: physical activity 
Words: roll, stoop, autumn, fall, drop

autumn