Thick And Thin Meaning

(idiomatic) Both good and bad times.

Example: Both thickets and thin woodland; (through) all obstacles in a path.
c. 1390, Geoffrey Chaucer, "The Reeve's Tale", Canterbury Tales, Ellesmere ms:
  Toward the fen / ther wilde Mares renne / fforth with wehee / thurgh thikke and thurgh thenne […]
1590, Edmund Spenser, The Faerie Queene, III.1:
  His tyreling Jade he fiersly forth did push / Through thicke and thin, both over banck and bush […]
  "I must follow him through thick and thin." - Miguel de Cervantes[1]
  Through thick and thin she followed him.
  He became the panegyrist, through thick and thin, of a military frenzy.