Crotchet

A crotchet is the name of a musical note, often worth one beat or pulse.

What I didn’t know until I read “The Way of All Flesh” was that it also meant a whimsical fancy, a peculiar notion held by an individual in opposition to popular opinion.
...he inflicted them on his old friends, week by week becoming more entête with himself and his own crotchets. - Samuel Butler

Another definition for a crotchet is a hook: a sharp curve or crook; a shape resembling a hook or a small tool or hooklike implement.