"I love the Brooks which down their channels fret..."See in text(Ode Intimations of Immortality from Recollections of Early Childhood)
This is an inspired description of a typical mountain brook. The waters seem to "fret" because there are so many twists, turns, and obstacles in the way. The word "fret" as used here suggests haste, impatience, and frustration.
Hamlet uses the word "fret" as a double entendre when reprimanding Guildenstern in act III, scene II of Hamlet:
'Sblood, do you think I am easier to be played on than a pipe? Call me what instrument you will, though you can fret me, yet you cannot play upon me.
Fret bars on musical instruments such as guitars are designed for ease of fingering. Hamlet feels "fretted" and "fretful" because he is being badgered by many people, including Polonius—and now again by Guildenstern.
